A NEW PHYLOGENY OF THE CARNIVOROUS DINOSAURS Thomas R. HOLTZ, Jr. A : The last several years have seen the discovery of many new theropod dinosaur taxa. Data obtained from these and from fragmentary forms not previously utilized in cladis- tic analyses are examined. An analysis of forty one primary ingroup taxa and 386 characters yielded a set of most parsimonious cladograms which preserves many previously discov- ered relationships (e.g., a basal split between Ceratosauria and Tetanurae; a carnosaur- coelurosaur clade Avetheropoda outside of more primitive "megalosaur" - grade teta- nurines; Dromaeosauridae as the sister taxon to birds, and so forth). The Middle Jurassic English Proceratosaurus was discovered to be a basal coelurosaur, as was (on less secure evidence) the Middle Jurassic Chinese Gasosaurus: these are among the oldest coeluro- saurs yet described. Several characters previously considered to be restricted to birds and other advanced coelurosaurs (e.g., furcula, semilunate carpal block) were found to be more broadly distributed among tetanurines. Other characters, once considered synapomor- phies for Avetheropoda (e.g., loss of metacarpal IV, possession of a pubic obturator notch) were found to be convergent between advanced carnosaurs and advanced coelurosaurs, lacking in the basal members of both clades. At least three (and possibly four) separate ori- gins for the arctometatarsalian pes were supported in this study. The mosaic of derived character state distributions for troodontids relative to the dromaeosaurid-bird clade, the tyrannosaurid-ornithomimosaur clade, and the therizinosauroid-oviraptorosaur clade sug- gests that relationships alternative to the most parsimonious found here may be supported in future studies. INTRODUCTION Since the pioneering work of GAUTHIER (1986), there has been great scientific interest in the phy- logeny of the Theropoda MARSH, 1881. Much of this interest stems from the recognition that the origin of birds lies within the theropod dinosaurs, an hypothe- sis advanced by OSTROM (e.g., 1974, 1975a, 1975b, 1976) primarily from his work on the dromaeosaurid Deinonychus antirrhopus OSTROM, 1969a (see PA- DIAN &CHIAPPE, 1998 for a recent review of bird ori- gins). The results of Gauthier's phylogenetic analysis are shown in Fig. 1A, B. Numerous authors have proposed phylogenetic hypotheses subsequent to Gauthier's initial 1986 study: BAKKER,WILLIAMS &CURRIE, 1988; NOVAS, 1992, 1997a; CURRIE &ZHAO, 1993a; RUSSELL & DONG, 1993a, b; PÉREZ-MORENO et al., 1993, 1994; HOLTZ, 1994, 1995a, 1996a; SERENO et al., 1994, 1996, 1998; SERENO, 1997, 1998; SUES, 1997; HAR- RIS, 1998; FORSTER et al. 1998; MAKOVICKY &SUES, 1998. Results of some of these studies are pre- sented in Fig. 1. The present analysis attempts to synthesize the proposed phylogenetic data from these studies, be- ginning as an update of previous work by the present author (HOLTZ, 1994). Among the changes from that work include correction of typographical errors in the character descriptions and elimination or modifica- tion of poorly coded characters (see CLARK,PERLE &NORELL, 1994; HUTT,MARTILL &BARKER, 1996; CHARIG &MILNER, 1997; NORELL &MAKOVICKY, 1997 for specific examples). Furthermore, many significant new theropod taxa and more complete remains of hitherto poorly known forms (therizino- sauroids, basal ornithomimosaurs, spinosaurids, sinraptorids, alvarezsaurids, etc.) which were not previously used have been incorporated into the new analysis. Additionally, new characters drawn from the studies listed previously are included (some in a modified form) here, as are some previ- ously unused characters. To fully describe each of the characters in this study in detail will require a much longer work (in preparation by the present author). This paper, how- 5 artigos/papers
Transcript
A NEW PHYLOGENY OF THE CARNIVOROUSDINOSAURS
Thomas R. HOLTZ, Jr.Department of Geology, University of Maryland. College Park, MARYLAND 20735. USA
ABSTRACT: The last several years have seen the discovery of many new theropod dinosaurtaxa. Data obtained from these and from fragmentary forms not previously utilized in cladis-tic analyses are examined. An analysis of forty one primary ingroup taxa and 386 charactersyielded a set of most parsimonious cladograms which preserves many previously discov-ered relationships (e.g., a basal split between Ceratosauria and Tetanurae; a carnosaur-coelurosaur clade Avetheropoda outside of more primitive "megalosaur" - grade teta-nurines; Dromaeosauridae as the sister taxon to birds, and so forth). The Middle JurassicEnglish Proceratosaurus was discovered to be a basal coelurosaur, as was (on less secureevidence) the Middle Jurassic Chinese Gasosaurus: these are among the oldest coeluro-saurs yet described. Several characters previously considered to be restricted to birds andother advanced coelurosaurs (e.g., furcula, semilunate carpal block) were found to be morebroadly distributed among tetanurines. Other characters, once considered synapomor-phies for Avetheropoda (e.g., loss of metacarpal IV, possession of a pubic obturator notch)were found to be convergent between advanced carnosaurs and advanced coelurosaurs,lacking in the basal members of both clades. At least three (and possibly four) separate ori-gins for the arctometatarsalian pes were supported in this study. The mosaic of derivedcharacter state distributions for troodontids relative to the dromaeosaurid-bird clade, thetyrannosaurid-ornithomimosaur clade, and the therizinosauroid-oviraptorosaur clade sug-gests that relationships alternative to the most parsimonious found here may be supportedin future studies.
INTRODUCTION
Since the pioneering work of GAUTHIER (1986),there has been great scientific interest in the phy-logeny of the Theropoda MARSH, 1881. Much of thisinterest stems from the recognition that the origin ofbirds lies within the theropod dinosaurs, an hypothe-sis advanced by OSTROM (e.g., 1974, 1975a, 1975b,1976) primarily from his work on the dromaeosauridDeinonychus antirrhopus OSTROM, 1969a (see PA-DIAN & CHIAPPE, 1998 for a recent review of bird ori-gins). The results of Gauthier's phylogeneticanalysis are shown in Fig. 1A, B.
Numerous authors have proposed phylogenetichypotheses subsequent to Gauthier's initial 1986study: BAKKER, WILLIAMS & CURRIE, 1988; NOVAS,1992, 1997a; CURRIE & ZHAO, 1993a; RUSSELL &DONG, 1993a, b; PÉREZ-MORENO et al., 1993, 1994;HOLTZ, 1994, 1995a, 1996a; SERENO et al., 1994,1996, 1998; SERENO, 1997, 1998; SUES, 1997; HAR-RIS, 1998; FORSTER et al. 1998; MAKOVICKY & SUES,1998. Results of some of these studies are pre-sented in Fig. 1.
The present analysis attempts to synthesize theproposed phylogenetic data from these studies, be-ginning as an update of previous work by the presentauthor (HOLTZ, 1994). Among the changes from thatwork include correction of typographical errors in thecharacter descriptions and elimination or modifica-tion of poorly coded characters (see CLARK, PERLE& NORELL, 1994; HUTT, MARTILL & BARKER, 1996;CHARIG & MILNER, 1997; NORELL & MAKOVICKY,1997 for specific examples). Furthermore, manysignificant new theropod taxa and more completeremains of hitherto poorly known forms (therizino-sauroids, basal ornithomimosaurs, spinosaurids,sinraptorids, alvarezsaurids, etc.) which were notpreviously used have been incorporated into thenew analysis. Additionally, new characters drawnfrom the studies listed previously are included(some in a modified form) here, as are some previ-ously unused characters.
To fully describe each of the characters in thisstudy in detail will require a much longer work (inpreparation by the present author). This paper, how-
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GAIA Nº 15, LISBOA/LISBON, DEZEMBRO/DECEMBER 1998, pp. 5-61 (ISSN: 0871-5424)
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Fig. 1 - Previously proposed phylogenies of theropod relationships. Taxonomy of listed forms revised to match thenames used here. A - Cladogram of comparatively well known theropods from GAUTHIER (1986). B - Cladogram of alltheropods included in GAUTHIER (1986), dashed line for Ornithomimosauria represents topology from GAUTHIER (1986),solid line after WILKINSON (1995) (differs from that presented in GAUTHIER (1986) due to incomplete computational analy-sis in that study: see WILKINSON (1995) for details). C - BAKKER, WILLIAMS & CURRIE (1988). D - NOVAS (1992).E - RUSSELL & DONG (1993a). F - PÉREZ-MORENO et al. (1993). G - HOLTZ (1994). (Continued)
(Dromaeosauridae
To fully describe each of the characters in thisstudy in detail will require a much longer work (inpreparation by the present author). This paper, how-ever, will serve as an interim study pending thatmore detailed phylogenetic analysis.
METHODS AND MATERIALS
The operational taxonomic units (OTUs) em-ployed in this study are listed in TABLE I. Forty one in-group taxa were used in the primary analysis. Thephylogenetic positions of three very fragmentaryforms (Deltadromeus agilis, "Megalosaurus" hes-
peris, and Unenlagia comahuensis) were examinedin subsequent analyses.
The sister taxon to those theropods used here isa matter of some recent debate. NOVAS (1994,1997b), SERENO (1997, 1998), and SERENO & NO-VAS (1992, 1994) have proposed that the Late Trias-sic taxa Eoraptor lunensis SERENO et al., 1993 ofArgentina and the more globally distributed Herre-rasauridae BENEDETTO, 1973 share a more recentcommon ancestor with the taxa used in this analysisthan do any other known forms (Fig. 2A). Under thisphylogeny, Eoraptor and the herrerasaurids would
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Fig. 1 (continued) - Previously proposed phylogenies of theropod relationships. Taxonomy of listed forms revised tomatch the names used here. H - PÉREZ-MORENO et al. (1994). I - SERENO (1997, 1998). J - FORSTER et al. (1998).K - MAKOVICKY & SUES (1998).
1 -PAUL (1988),SMITH (1998),CHURE (1998),HENDERSON (1998) andBAKKER (1998) argue thatmore thanonespecies (or higher leveltaxa) are present in the Morrison Formation genus Allosaurus. 2 - WELLNHOFER (1993) suggests that two species are present in theSolnhofen Lithographic Limestone genus Archaeopteryx: A. lithographicaMEYER, 1861 and A. bavaricaWELLNHOFER, 1993. 3 - Sin-raptor includes two species, S. dongi CURRIE & ZHAO, 1993a and S. hepingensis (GAO, 1992). 4 - Yangchuanosaurus includes twospecies, Y. shangyouensis DONG, CHANG, LI & ZHOU, 1978 and Y. magnus DONG, ZHOU & ZHANG, 1983.
phylogeny, Eoraptor and the herrerasaurids wouldbe considered true theropods (given the definition ofTheropoda following GAUTHIER (1986): birds and alltaxa sharing a more recent common ancestor withbirds than with sauropodomorphs). Among the po-tential derived characters supporting such an hy-pothes is are prominent pos tax ia l cerv ica lepipophyses; greatly reduced manual digits IV andV; an intramandibular joint; and a distal enlargementof the pubis (NOVAS, 1994, 1997a; SERENO, 1997).
Alternatively, HOLTZ & PADIAN (1995) and BONA-PARTE & PUMARES (1995) have argued that sauro-podomorphs share a more recent common ancestorwith the forms in this analysis than do Eoraptor orherrerasaurids (Fig. 2B). Derived characters sup-porting such an hypothesis include pollex unguallarger than other manual unguals; manual digit IIlongest digit in the hand; vertebrae 6-9 longest in thecervical column; and a distal expansion of the is-chium.
The question of the sister taxon to the forms usedhere is the subject of a separate study by the presentauthor and PADIAN, in preparation. For this analysis,a compromise outgroup was used. Character statesshared in common in Eoraptor, herrerasaurids, and
basal sauropodomorphs (as well as those in com-mon in all three of these and in more distantly relatedforms such as ornithischians, basal ornithodirans,and non-ornithodiran archosauriforms) were con-sidered to the primitive relative to the taxa in the cur-rent study. Character states found in the taxa in thepresent analysis and in some (but not all three) ofEoraptor, herrerasaurids, and basal sauropodo-morphs were coded as derived for the ingroupforms: these are discussed below. Finally, characterstates found in some or all of the ingroup taxa butnone of the three potential sister taxa are coded asderived. Based on these codings, an "all zero" out-group with all primitive states was created to ap-proximate a compromise ancestral condition. Thecharacter states observed in herrerasaurids (pri-marily Herrerasaurus) and basal sauropodomorphs("prosauropods") are also included here, and use ofthese taxa rather than an "all zero" outgroup arebriefly discussed. In the longer study in preparationby the present author, differences between the re-sults using this method and various arrangements ofthe known potential outgroups will be examined.
The characters employed in this analysis arelisted in APPENDIX I. 386 characters were used (135craniodental, 75 axial, 74 pectoral and forelimb, and102 pelvic and hindlimb characters). 301 of the char-acters are coded as binary; 85 as multistate. All bi-nary characters were considered unordered;multistate characters were considered unorderedunless otherwise indicated (see APPENDIX I). De-scriptors of facial pneumatic structures follow WIT-MER (1997). In APPENDIX I a brief description of theprimitive and derived state(s) is provided; in work inpreparation, each of these characters will be de-scribed in greater detail (as in GRANDE & BEMIS(1998) or WILSON & SERENO (1998)). However,some characters of particular phylogenetic signifi-cance in this or previous studies will be discussedbelow. APPENDIX II is the data matrix analyzed.
The resulting data matrix was analyzed usingPAUP 3.1.1 (SWOFFORD, 1993). The unwieldy sizeof the data matrix required the use of the Heuristicsearch option, as the Branch-and-Bound and Ex-haustive search methods would require prohibitivelylong run times given current computer calculationspeeds. In all cases, random branch addition wasrun with thirty replicates, to reduce the chance offalsely accepting a local rather than global minimum(that is, a tree or set of trees with less than maximumparsimony). The set of most parsimonious trees dis-covered under these runs was analyzed using Mac-Clade 3.07 (MADDISON & MADDISON, 1997), in orderto determine character state distribution under ac-celerated and delayed transformation (ACCTRANand DELTRAN, respectively) optimizations and toexamine alternate topologies. The tree length, con-
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Fig. 2 - Alternative phylogenies for sister taxon to thero-pods used in this study. A - Herrerasaurids and Eoraptorshare a more recent common ancestor with (more ad-vanced) theropods than do sauropodomorphs, afterNOVAS (1994, 1997a), SERENO (1997, 1998), and SERENO& NOVAS (1992, 1994). B - Sauropodomorphs share amore recent common ancestor with theropods than do ei-ther herrerasaurids or Eoraptor, after HOLTZ & PADIAN(1995) and BONAPARTE & PUMARES (1995).
sistency index (CI), retention index (RI), and res-caled consistency index (RC) for each tree was cal-culated on MacClade, while the homoplasy index(HI) was calculated on PAUP: see pp. 364-368 ofMADDISON & MADDISON (1997) for the differences inmetric calculations between these two programs.Bremer support values were calculated by means ofthe AutoDecay program, version 4.0 (ERIKSSON,1998).
Names of clades found in this analysis are basedon the standardized phylogenetic definitions pro-vided in PADIAN, HUTCHINSON & HOLTZ (1999), andare summarized in TABLE II. See the referenceabove, SERENO (1998), and the references thereinfor a discussion of the principles of phylogenetic tax-onomy. SERENO (1997, 1998) provides some differ-ent definitions for the same names, and somedifferent names for the same definitions as usedhere: see PADIAN, HUTCHINSON & HOLTZ (1999) fordiscussion of these taxonomic conflicts.
RESULTS
The primary analysis produced a set of 20equally parsimonious trees of 1404 steps. The CI forthese trees was 0.442, the RI was 0.618, the RC was0.273, and the HI was 0.647. The strict consensus ofthese trees is presented in Fig. 3A. The normalizedconsensus fork index, a measure of consensus treeresolution (number of nodes in the strict consensustree over number of nodes in a fully resolved di-chotomous tree of the same number of taxa:COLLESS, 1980) is 0.825. Use of Herrerasauridae asan outgroup does not alter tree topology, but insteadproduces the same 20 trees at a tree length of 1412,a CI of 0.439, an RI of 0.614, an RC of 0.269, and anHI of 0.649. Use of basal sauropodomorphs ("pro-sauropods") yields 120 trees of tree length 1458, CI0.433, RI 0.619, RC 0.268, and HI 0.658: the tree to-pologies are identical to those analyses using the allzero outgroup or the herrerasaurid outgroup, exceptthat Megalosaurus, Torvosaurus, Eustreptospondy-
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TABLE IIPhylogenetic taxonomic definitions used in this study, based primarily on PADIAN, HUTCHINSON& HOLTZ (1999)
Taxon, taxon type, and reference taxa for phylogenetic definitions employed in this paper.Definitions and justifications discussed inPA-DIAN, HUTCHINSON &HOLTZ (1999). Type: Stem, stem-based; Node, node-based. Stem-based taxon definitions are of the form "refer-ence taxon A and all taxa sharing a more recent common ancestor with reference taxon A than with reference taxon B". Node-basedtaxon definitions are of the form "all descendants of the most recent common ancestor of reference taxa A and B."
lus, and Piatnitzkysaurus are equally parsimoni-ously placed in six different possible configurationsrelative to the Afrovenator-avetheropod clade. Theincrease in tree length and decrease in CI, RI, RC,and HI is explained by homoplasy in some condi-tions found in herrerasaurids or prosauropods andvarious derived theropod clades, but not hypothe-sized for basal neotheropods under either acceler-ated or delayed transformation.
Examination of the resulting trees in the primaryanalysis (using the all zero outgroup) found that thepolytomies in the strict consensus cladogram couldbe decomposed as instability at three different re-gions. The variability at each these three regions isindependent of the variability at the other three. Thisindependence (five different possible topologies inone region of the tree, two in the other two) results inthe 20 different equally parsimonious trees recov-ered.
In the first of these cases, the instability occurredbecause of the incompletely known taxon Procera-tosaurus bradleyi, known only from cranial remainsfrom the Middle Jurassic (Bathonian) of England,was found to occupy five different possible positionswith respect to the other basalmost coelurosaursGasosaurus and Dryptosaurus without change intree length, CI, or other tree metrics (Fig. 3B). Thesecond region of tree instability concerns two alter-native placements for the fragmentary Aptian-Albian form Microvenator celer, as either the sistertaxon to Oviraptoridae or the sister taxon to the cladeOviraptoridae plus Caenagnathidae (Fig. 3C).
The third instability is of greater interest, as it con-cerns two alternative placements of the well knowntaxon Troodontidae as the sister group to two verydifferent clades: a sister group relationship with thedromaeosaurid-bird clade on the one hand, and asister group relationship with Ornithomimosauria onthe other. Both topologies are equally parsimonious,and result in the apparent lack of resolution amongmaniraptoriform coelurosaurs shown in Fig. 3A. Infact there is much greater structure than revealedunder strict consensus: all the other taxa have re-solved positions relative to each other, with the ex-ception of Troodontidae itself. The structure withinManiraptoriformes is presented in Fig. 4, whichshows the two alternative positions for troodontids.
A summary cladogram (Fig. 5) is used to discussthe distribution of characters in the present analysis.This represents one of the twenty most parsimoni-ous trees in the analysis. For this summary clado-gram, Proceratosaurus was placed betweenGasosaurus and Dryptosaurus, and Microvenatorplaced as outside of an oviraptorid-caenagnathidclade (the position preferred by the lower stra-tigraphic position of this form). A tree in which Troo-
dontidae is more closely related to dromaeosauridsand birds than to ornithomimosaurs was selected forthe summary cladogram, as this topology moreclosely reflects the results of most other workers(e.g., GAUTHIER, 1986; NOVAS, 1992; SERENO,1997, 1998; SUES, 1997; MAKOVICKY & SUES, 1998;FORSTER et al., 1998; NOVAS & POL, in press). How-ever, the analyses of HOLTZ (1994) and PÉREZ-MORENO et al. (1994) (and previously the non-numerical study of THULBORN (1984)) recovered atroodontid-ornithomimosaur clade to the exclusionof dromaeosaurids or birds, which represents the al-
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Fig. 3 - Relationships among theropod dinosaursbased on maximum parsimony analysis of 386 morpho-logical characters. A - Tree represents the strict consen-sus of twenty equally most parsimonious trees (treelength=1404, CI=0.442, RI=0.618, RC=0.273, HI=0.647,normalized consensus fork index=0.825). Charactersused in analysis included in Appendix I. B - Dashed linesindicate the five equally parsimonious alternative positionsof Proceratosaurus (Pr.) relative to Gasosaurus (Gaso.)and Dryptosaurus (Drypto.). C - Dashed lines indicate thetwo equally parsimonious alternative positions of Microve-nator (Micro.) relative to Oviraptoridae (Ovir.) andCaenagnathidae (Caen.).
ternative topology of this study. Characters support-ing this position will be discussed below.
Note that this particular configuration (Fig. 5) isused to facilitate discussion only, and is not pre-ferred by the data analysis over the nineteen otherpotential arrangements. Future analyses may helpto resolve the uncertainty with regards to the rela-tionships presented here (if not overturn some or allof those in the current analysis, pending the additionof new data).
Addition of the fragmentary Deltadromeus of theCenomanian of northern Africa results in 80 equallyparsimonious trees two steps longer than the pri-mary analysis (tree length 1406, CI 0.441, RI 0.618,RC 0.272, HI 0.627). This addition does not changethe tree topology: rather, Deltadromeus is equallyparsimoniously placed in five different positions.These positions are: as the sister taxon to Orni-tholestes; as the sister taxon to Coelurus, or as thesister taxon to nodes ff, gg, or jj. Similarly, inclusionof the poorly known Unenlagia of the Late Creta-ceous of Argentina does not alter overall tree struc-ture. Instead, its presence results in a total of 50trees eleven steps longer (tree length 1415, CI0.438, RI 0.619, RC 0.271, HI 0.649) than that in theprimary analysis. Unenlagia is equally parsimoni-ously placed as the sister taxon to Rahonavis, as thesister taxon to the Archaeopteryx-Metornithes clade(node mm), or as the sister group to Ornithothora-ces. Inclusion of "Megalosaurus" hesperis (knownonly from cranial material of the Middle Jurassic of
England) results in 220 trees 1 step longer than theprimary analysis (TL 1405, other metrics identical tomain analysis). "M." hesperis is equally parsimoni-ously placed as the sister group to nodes G, H, I, J, K,or L or as the sister group to Spinosauridae, Megalo-saurus, Eustreptospondylus, Torvosaurus, or Piat-nitzkysaurus.
In the following section, the character statesfound at each node are listed. The nodes are listedby the corresponding letter from the summary clado-gram (Fig. 5). Taxon names are listed for some of theclades mentioned here, following the definitions pro-posed in PADIAN, HUTCHINSON & HOLTZ (1999), andlisted in TABLE II. Stem-defined names are under-lined in the description headings, whereas node-defined names are not. Where two names are listed,the first represents the stem-defined taxon nameand the second is the node-defined taxon name. Notall nodes are named.
For purposes of description of the nodal charac-ter state changes, ALL refers to those derived char-acter states present in all optimizations, ACCTRANrefers to those derived character states present atthat node under accelerated transformation (i.e., atthe basalmost point on the tree where this charactercould appear without requiring additional evolution-ary steps), and DELTRAN refers to those present atthat node under delayed transformation (i.e., at theterminal-most point on the tree where this charactercould appear without requiring additional evolution-ary steps). Characters are listed by the characternumber (before the period) and state (after the peri-od): for example, 17.1 refers to the condition "maxil-lary fenestra present." Characters listed with aminus sign (-) before them represent a reversal to astate found at a more basal position in the tree: forexample, -17.0 would indicate "maxillary fenestraabsent" for a form nested within a clade otherwisecharacterized by the state 17.1.
NODE A. THEROPODA - NEOTHEROPODA
ALL: 10.1 Premaxilla and nasal do not meet sub-narially; 26.1 Narial prominences present; 30.1 Lac-rimal broadly exposed on skull roof; 45.1 Orbit ovalor key-shaped, rounded dorsally, constricted ven-trally; 54.1 Postorbital frontal process about samelevel or slightly higher than squamosal, producing T-shaped postorbital; 73.1 Vomera fused rostrally;110.1 Reduced overlap of dentary onto postdentarybones; 111.1 Intramandibular joint; 117.1 Rostralprong of angular penetrates the dentary-splenialcavity; 137.1 First intercentrum with large occipitalfossa (two or less times as wide as tall) and smallodontoid notch; 138.1 Second intercentrum cranialarticulation with first intercentrum with broad cres-centic fossa; 148.1 Postaxial cervical pleurocoels,one pair present; 152.1 Caudal cervical epipophy-
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Fig. 4 - Maniraptoriform theropod cladogram as recov-ered in this analysis. Solid lines indicate positions sharedby all twenty most parsimonious trees; dashed line indi-cates two equally parsimonious positions for Troodontidae(as bullatosaurian arctometatarsalians or as paravianmaniraptorans). See text for discussion.
ses elongate; 164.1 Longest postaxial cervicals VI-IX; 180.1 Cranial and median dorsal pleurocoels,one pair present; 181.1 Presacral pleurocoels cam-erate; 185.3 Number of sacrals five; 197.1 Transi-tion point in distal half of tail; 219.1 Coracoid bicepstubercle conspicuous and well developed; 256.3Metacarpal V absent; 257.1 Metacarpal IV present,without ungual; 270.1 Digit II longest in manus;271.1 Penultimate phalanx longest nonungual pha-lanx; 286.1 Ilium dolichoiliac; 290.1 Brevis fossadeep; 301.1 Acetabular height/craniocaudal length
about 50%; 312.1 Pubic blade at least six times aslong as broad; 329.1 Femur shape bowed in convexarc with less pronounced sigmoidality; 336.1 Proxi-malmost point of anterior trochanter below femoralhead; 372.1 Metatarsal V vestigial or absent; 378.1Metatarsal I reduced but retains phalanges; 379.1Metatarsal I placed near midpoint of metatarsal IIshaft.
ACCTRAN: 16.1 Promaxillary fenestra present,visible in lateral view; 24.1 Nasal participates in an-
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Fig. 5 - Summary cladogram of theropod relationships, representing one of the twenty equally parsimonious trees inthis analysis. See text for character state changes at each node, listed by letter indicated. Note that the topology shownhere is not preferred by the data over other potential topologies, but was instead chose to facilitate discussion of characterdistribution. See text for details. A - Ceratosauria and non-maniraptoriform Tetanurae section of tree. B - Maniraptorifor-mes.
torbital cavity; 44.1 Orbit shorter than internal antor-bital fenestra length; 58.1 Jugal participates ininternal antorbital fenestra; 67.1 Quadrate foramenreduced or absent; 81.1 Ventral ectopterygoid re-cess present and comma-shaped; 253.1 Distal car-pal I block does not overlap metacarpal II dorsally,but does so ventrally; 254.1 Distal carpal I fused todistal carpal II; 278.1 Pollex larger than other man-ual unguals; 317.2 Pubic boot rounded, angle be-tween shaft and caudal portion of boot acute; 319.1Pubic boot present, less than 30% as long as pubicshaft; 339.1 Muscle scar in craniodistal region of fe-mur present, non-elliptical in shape; 344.1 Ectocon-dylar tuber proximodistally long, pronounced, andextends almost to distal end of femur; 350.1 Cristafibularis present, not well developed.
DELTRAN: None
As defined by GAUTHIER (1986) Theropoda is astem-based taxon, comprised of birds and all taxasharing a more recent common ancestor with birdsthan with sauropodomorphs. The term Neothero-poda BAKKER, 1986 has been used by SERENO et al.(1993), SERENO (1997, 1998), and PADIAN,HUTCHINSON & HOLTZ (1999) for the node-definedtaxon comprised of all descendants of the most re-cent common ancestor of Ceratosauria and Tetanu-rae (or, more explicitly, of Ceratosaurus andNeornithes: see PADIAN, HUTCHINSON & HOLTZ(1999)).
How and if the diagnosis of Theropoda and Neo-theropoda differ hinges on the question of the imme-diate sister group of Neotheropoda (see above, andFig. 2). The following characters from the above listare shared by basal theropods and basal sauropo-domorphs, and would therefore diagnose a clademore inclusive than Theropoda if herrerasauridsand Eoraptor are not theropods themselves: 10.1,67.1, 117.1, 164.1, 270.1, 278.1, and 301.1. Thoseshared in common with Herrerasauridae and/orEoraptor (see below) would either have evolvedconvergently between these Triassic forms and truetheropods or have been present in the common an-cestor of these taxa, theropods, and sauropodo-morphs, and subsequently lost in the latter. Theremaining characters of the above list would be di-agnostic of Theropoda and Neotheropoda (whichwould share the same diagnosis, as all known thero-pods would be neotheropods).
If instead herrerasaurids and Eoraptor are truetheropods, then character 197.1 (Transition point indistal half of tail) would be considered synapomor-phic for Theropoda, and the following for anherrerasaurid-neotheropod clade: 67.1, 111.1,117.1, 138.1, and 152.1. It should be noted, how-ever, that the condition represented by characterstate 111.1 (Intramandibular joint) may not be ho-
mologous in Herrerasauridae and Neotheropoda,as SERENO & NOVAS (1994) noted the geometry ofthe joint are reversed between the two taxa: in herre-rasaurids, the splenial has a concave surface whichslides against the convex ventral margin of the an-gular, while in neotheropods the splenial has a con-vex dorsal surface which slides against a concavedepression on the angular (p. 471). No characterswere observed which were present in Eoraptor andbasally within Neotheropoda that were not alsofound in herrerasaurids. Under this scheme, theseven derived characters shared by neotheropodsand basal sauropodomorphs mentioned previouslywould either have had to developed independentlyin these two lineages, or have been present and sub-sequently lost in Eoraptor and Herrerasauridae.
There remain many characters found basally inCeratosauria and Tetanurae which are not alsofound in basal sauropodomorphs, Eoraptor, or Her-rerasauridae. These are diagnostic for Neothero-poda, regardless of either particular sister groupscenario.
NODE B. CERATOSAURIA
ALL: 31.2 Lacrimal prominences comprised ofridge continuous with raised surface of lateral edgeof nasals; 148.2 Postaxial cervical pleurocoels, twopairs present; 170.1 Dorsal transverse processesstrongly backturned caudally and triangular in dor-sal view; 180.2 Cranial and median dorsal pleuro-coels, two pairs present; 193.1 Ventral groove incranial caudals; 201.1 Shaft of cervical ribs ex-tremely long (four or more times centrum length) andslender; 291.2 Brevis fossa distal end broad; 300.1Supracetabular shelf on ilium present; 309.1 Pubisorientation propubic, proximal portion of shaft ap-proximately 30 degrees from horizontal; 321.1 Is-chial antitrochanter large; 335.1 Anterior trochanterconical prominence; 338.1 Trochanteric shelf of fe-mur well developed; 340.1 Medial epicondyle (=mediodistal crest) of femur pronounced, extendsone quarter or more the length of the femoral shaft;342.1 Groove in lateral condyle of femur; 345.1 Sul-cus along medial side of base of crista tibiofibularis;356.1 Sulcus in proximomedial region of fibula;359.1 Anterior surface of distal fibula overlaps as-cending process of astragalus cranially; 375.1Metatarsal III dorsal surface area clearly larger thaneither metatarsal II or metatarsal IV
ACCTRAN: 189.1 Synsacrum present in adults;285.1 Pelvic girdle sutures fused in adults; 366.1 As-tragalocalcaneum (astragalus fused to calcaneum)
DELTRAN: 24.1 Nasal participates in antorbitalcavity; 44.1 Orbit shorter than internal antorbital fen-estra length; 67.1 Quadrate foramen reduced or ab-
14
T.R. HOLTZ, JR.
sent; 319.1 Pubis and ischium proximal shaftsnarrow
As first proposed by GAUTHIER (1986), Cerato-sauria forms a major clade of theropods containingsuch forms as Ceratosaurus, Dilophosaurus, andCoelophysis. As in HOLTZ (1994), Ceratosauria is di-vided into two primary branches, the relativelygracile Late Triassic and Early Jurassic Coelophy-soidea and the more robust Late Jurassic and Creta-ceous Neoceratosauria.
ROWE (1989) and ROWE & GAUTHIER (1990) con-s idered the Ear ly Jurass ic (?Sinemur ian-Pliensbachian) Sarcosaurus woodi ANDREWS 1921to be a ceratosaur. This taxon (known only from apartial pelvis) was not included in the present analy-sis, so its relationship with other ceratosaurs is notresolved here.
NODE C. COELOPHYSOIDEA
ALL: 11.1 Subnarial gap; 26.2 Narial promi-nences comprised of paired ridges along lateraledges of nasals; 64.1 Dorsal ramus of quadratojugaldoes not contact squamosal; 142.1 Axial parapo-physes reduced; 143.1 Axial diapophyses absent;145.1 Axial pleurocoels absent; 151.1 Epipophyseson cervical vertebrae placed proximally; 234.1 Hu-meral torsion present; 235.1 Humeral shaft sigmoid;308.1 Pubic fenestra ventral to obturator foramen
ACCTRAN: 27.1 Paired crescentic crestsformed by nasal and lacrimal prominences; 127.1Dentary teeth more numerous and smaller thanmaxillary teeth; 331.1 Femoral head transverselyelongate
As in ROWE (1989), NOVAS (1992), HOLTZ (1994),and SERENO (1997), a clade comprised of Dilopho-saurus and the Coelophysis-Syntarsus clade (Coe-lophysidae) to the exclusion of other ceratosaurswas supported.
Paired crescentic crests formed by nasal and lac-rimal prominences may be synapomorphic for Coe-lophysoidea (SERENO, 1997) as they are present inDilophosaurus and Syntarsus kayentakatae ROWE1989 (although not in Coelophysis nor in Syntarsusrhodesiensis). Such crests were the primary evi-dence for placing "Dilophosaurus" sinensis HU,1993 in that genus: since these structures are foundin other coelophysoids, and given certain other de-rived anatomical differences between these taxa(tooth row rostral to the orbit in D. wetherilli, five pre-maxillary teeth in "D." sinensis, among others), itmay be that the Chinese taxon does not share amore recent common ancestor with Dilophosaurus
than with some other coelophysoid genus. ROWE(1989) found evidence that Liliensternus liliensterni(HUENE, 1934) was a coelophysoid (see alsoRAUHUT & HUNGENBÜHLER, 1998), as did SERENO(1997), who also included ProcompsognathusFRAAS, 1913 and Segisaurus CAMP, 1936 in thisclade. CARPENTER (1997) has described a largeLate Triassic North American coelophysoid Goji-rasaurus quayi. These taxa were not included in thisstudy: future analyses will hopefully clarify the rela-tionships of these taxa to each other and to otherceratosaurs.
The Late Jurassic African Elaphrosaurus bam-bergi does share numerous derived features withcoelophysoids in general, and coelophysids in par-ticular (e.g., 154.1, 160.1, 165.1, 376.2). UnlikePAUL (1988) and NOVAS (1992), Elaphrosaurus wasnot found to be member of Coelophysoidea in thisanalysis, but rather was hypothesized to share amore recent common ancestry with abelisauroidsand Ceratosaurus, as in HOLTZ (1994) and SERENO(1997). However, moving this taxon to a sister groupposition with node C or with Coelophysidae requiresonly one additional evolutionary step, and additionaldetails may reveal that Elaphrosaurus was a late-surviving coelophysoid. (See also Discussion).
The newly discovered taxon Genusaurus serusACCAIRE et al., 1995 was considered by thoseauthors to be a ceratosaur closer to Coelophysisthan to Ceratosaurus. If such a position were con-firmed, it would indicate the first known Cretaceous(middle Albian) coelophysoid. However, althoughthis form demonstrates some ceratosaurian fea-tures (pelvic girdle sutures fused, proximal portion ofpubic shaft approximately 30 degrees from the hori-zontal, trochanteric shelf well developed, sulcusalong medial side of base of crista tibiofibularis), itdoes not show any unambiguously coelophysoidfeature. In fact, a well-excavated proximal region ofthe fibular medial face is not known in coelophy-soids, but is documented in the neoceratosaur Car-notaurus. Additional study may demonstrateGenusaurus to be a mid-Cretaceous European abe-lisauroid.
NODE D. NEOCERATOSAURIA
ALL: 149.1 Cervical epipophyses powerfully de-veloped and prong-shaped; 185.4 Six sacrals.
ACCTRAN: 4.1 Premaxillary symphyseal regionU-shaped in ventral view; 5.1 Premaxilla subnariallyvery deep, main body taller dorsoventrally than longrostrocaudally; 62.1 Infratemporal fenestra abouttwice as large as the area of the orbit in lateral view;66.1 Quadrate-quadratojugal suture fused; 68.1Quadrate dorsal ramus greater than height of orbit;70.1 Quadrate articulation projects well caudal to
15
A NEW PHYLOGENY OF THE CARNIVOROUS DINOSAURS
the caudal point of the occipital condyle; 83.1 Nuchalcrest pronounced; 84.1 Supraoccipital with very pro-nounced, strongly demarcated median ridge on oc-cipital surface; 103.1 Occipital condyle constrictedneck; 116.1 Horizontal shelf on lateral surface ofsurangular, rostral and ventral to the mandibularcondyle, prominent and extends laterally; 144.1 Ax-ial epipophyses prominent; 181.2 Presacral pleuro-coels camellate; 231.1 Ulna/femur length ratio lessthan 28%; 232.1 Radius/humerus length ratio lessthan 50%; 315.2 Pubic boot rounded, angle be-tween shaft and caudal portion of boot acute; 355.1Proximal region of fibular medial face shallow andnot conspicuous.
DELTRAN: 189.1 Synsacrum present in adults;285.1 Pelvic girdle sutures fused in adults; 366.1 As-tragalocalcaneum (astragalus fused to calcaneum);376.2 Metatarsal III dorsal surface dumbbell shaped(cranial and (especially) plantar surfaces expandedto slightly overlap surfaces of metatarsals II and IV).
NODE E.
ALL: 147.1 Cervical centra surfaces markedlyopisthocoelous; 150.1 Cervical epipophyses di-rected dorsolaterally and taller than neural spine;185.5 More than six sacrals; 186.1 Sacrals III-Vtransversely compressed; 302.1 Ilium about as longas femur; 334.1 Anterior trochanter present, sepa-rated from femoral head by cleft; 337.1 Fourth tro-chanter of femur present, but little developed.
ACCTRAN: 357.1 Cranial protuberance on fibulabelow expansion.
DELTRAN: 4.1 Premaxillary symphyseal regionU-shaped in ventral view; 5.1 Premaxilla subnariallyvery deep, main body taller dorsoventrally than longrostrocaudally; 58.1 Jugal participates in internalantorbital fenestra; 62.1 Infratemporal fenestraabout twice as large as the area of the orbit in lateralview; 68.1 Quadrate dorsal ramus greater thanheight of orbit; 70.1 Quadrate articulation projectswell caudal to the caudal point of the occipital con-dyle; 83.1 Nuchal crest pronounced; 84.1 Supraoc-cipital with very pronounced, strongly demarcatedmedian ridge on occipital surface; 103.1 Occipitalcondyle constricted neck; 116.1 Horizontal shelf onlateral surface of surangular, rostral and ventral tothe mandibular condyle, prominent and extends lat-erally; 144.1 Axial epipophyses prominent; 160.2Midcervical centra length less than twice diameter ofcranial face; 315.2 Pubic boot rounded, angle be-tween shaft and caudal portion of boot acute; 317.2Pubic boot rounded, angle between shaft and cau-dal portion of boot acute; 339.1 Muscle scar incraniodistal region of femur present, non-elliptical inshape.
NODE F. ABELISAUROIDEA - ABELISAURIDAE
ALL: 15.2 Maxillary antorbital fossa greatly re-duced in size, not extending much beyond rim of theexternal antorbital fossa; 26.3 Narial prominencesknobby rugosities across dorsal and lateral surfaceof nasals, extending onto dorsalmost surface ofmaxillae; 35.2 Lacrimal dorsal (= rostral) ramus ab-sent; 37.1 Prefrontals reduced or absent; 41.1Frontal-frontal suture fused; 42.2 Frontal-parietalsuture on dorsal surface of skull fused, suture indis-tinguishable; 50.1 Postorbital-lacrimal contactbroad; 53.1 Postorbital suborbital flange
ACCTRAN: -117.0 Rostral prong of angular doesnot penetrate the dentary-splenial cavity; 161.1 Mid-cervical centra greater than 20% broader than tall;176.1 Dorsal centrum transverse section wider thanhigh; 188.1 Sacral neural spines fused to form lam-ina; 211.1 Scapular blade long, slender (four timesor more longer than midshaft width) and strap-like;212.1 Distal expansion of scapula reduced, lessthan width of proximal end of scapula; 213.1 Acro-mion in scapula reduced; 229.1 Humerus/scapulalength ratio less than 65%; -234.0 Humeral torsionabsent; 237.1 Internal tuberosity on proximal end ofhumerus well differentiated and angular; 249.1 Ul-nar facet for radius transversely expanded and con-cave; 269.1 Metacarpal-phalangeal joints nothyperextensible, extensor pits on metacarpals I-IIIreduced; 304.1 Iliac-ischial articulation smaller thaniliac-pubic articulation; -309.0 Pubis orientation pro-pubic, shaft approximately 45 degrees from horizon-tal; 330.1 Femoral head approximately 90 degreesfrom shaft (head directed horizontally); 355.2 Proxi-mal region of fibular medial face well excavated
As in NOVAS (1992), HOLTZ (1994), and SERENO(1997, 1998), a clade comprised of Ceratosaurusand abelisaurids was supported here. As in the stud-ies by the latter two authors, Elaphrosaurus wasfound to be part of this clade. However, as notedabove, support for a coelophysoid placement of thistaxon is nearly as strong.
As HOLTZ (1994) noted, many features unitingneoceratosaurs are also found in tetanurines: underthe most parsimonious distributions of derived char-acter states, these are explainable either as conver-gences between Neoceratosauria and Tetanurae oras basal neotheropod characters subsequently lostin Coelophysoidea. Alternatively, Ceratosaurus andAbelisauridae may share a more recent common an-cestor with tetanurines than with Coelophysoidea:however, such a phylogenetic scenario requiresseveral additional steps given the present data base(see Discussion below).
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T.R. HOLTZ, JR.
Although this study did not examine various otherneoceratosaurs, CORIA & SALGADO (1998) describea new taxon assignable to this clade. That study de-tails several forms that would belong to the stem-based taxon Abelisauroidea (all taxa sharing a morerecent common ancestor with Carnotaurus than withCeratosaurus) which were not included in this analy-sis, as well as additional character evidence for rela-tionships within Neoceratosauria. SAMPSON et al.(1998) have described excellent, well-preserved re-mains of the abelisaurid Majungatholus atopusSUES & TAQUET, 1979, a form which they considerlikely to be the sister taxon to Carnotaurus withinAbelisauridae. This new material will greatly in-crease our knowledge of neoceratosaur osteology.
NOVAS (1997c) has suggested that Carcharo-dontosaurus and Giganotosaurus were abeli-saurids or abelisaurid relatives. Such a relationshipwas not supported here, but is discussed below.
NODE G. TETANURAE
ALL: 13.1 Rostral ramus of maxilla present, dra-matic change in curvature of rostrodorsal surface ofmaxilla rostral to dorsal ramus forming concave sur-face; 14.2 Rostral ramus as long or longer rostro-caudally as dorsoventrally; 34.1 Slot in ventralprocess of lacrimal for jugal; 35.1 Lacrimal dorsal(rostral) ramus dorsoventrally pinched and narrow;133.1 Caudalmost maxillary tooth position rostral toorbit; 147.1 Cervical centra surfaces opisthocoel-ous; 211.1 Scapular blade long, slender (four timesor more longer than midshaft width) and strap-like;212.1 Distal expansion of scapula reduced, lessthan width of proximal end of scapula; 240.1 Hu-meral ends well expanded, greater than 150% mid-shaft diameter; 304.1 Iliac-ischial articulationsmaller than iliac-pubic articulation; 305.1 Pubic pe-duncle of ilium more developed craniocaudally thanmediolaterally; 341.1 Extensor groove in craniodis-tal region of femur present, but shallow and not con-spicuous; 352.1 Tibia distal end expanded to backcalcaneum; 362.1 Astragalar ascending processmediolaterally reduced, craniocaudally wide, andproximodistally low ("allosauroid condition")
ACCTRAN: 38.1 Prefrontal-frontal peg-in-socket suture; 48.1 Postorbital ventral processbroader transversely than rostrocaudally with U-shaped cross-section; 61.1 Jugal recess; 64.2Broad contact between dorsal ramus of quadratoju-gal and lateroventral ramus of squamosal; 76.1Palatine tetraradiate; 78.1 Palatine recesses; 123.1Retroarticular process of articular faces caudally;197.2 Transition point in proximal half of tail; 215.1Scapulacoracoid cranial margin with pronouncednotch between acromial process and coracoid;221.1 Sternal plates fused medially; 222.1 Sternumcarina present; 223.2 Sternum wider mediolaterally
than long craniocaudally; 225.1 Furcula; 233.1 Ma-nus/(humerus + radius) length ratio greater than66%; 255.1 Semilunate carpal block fully developedwith transverse trochlea; 257.2 Metacarpal IV pres-ent, without phalanges; 261.1 Articular surface be-tween metacarpals I and II extends well intodiaphysis of metacarpal I; 263.1 Metacarpal IIIclearly shorter than metacarpal II; 268.1 MetacarpalIV less than half length of metacarpal II; 279.1 Pollexungual greater than three times longer than height ofarticular facet; 283.1 Manual ungual length ex-tremely long; 334.1 Anterior trochanter present,separated from femoral head by cleft; 346.1 Cne-mial process arises out of the lateral surface of tibialshaft; 351.1 Crista fibularis proximally placed; 353.1Fibula closely appressed to tibia throughout mainshaft; 360.1 Fibula distal end less than twice cranio-caudal width at midshaft, and consequently astraga-lar cup for fibula reduced; 364.1 Astragalar distalcondyles oriented cranioventrally
DELTRAN: 16.1 Promaxillary fenestra present,visible in lateral view; 160.2 Midcervical centralength less than twice diameter of cranial face; 291.1Brevis fossa distal end tapered; 338.2 Trochantericshelf of femur absent; 339.1 Muscle scar in cranio-distal region of femur present, non-elliptical inshape; 301.1 Crista fibularis present, not well devel-oped; 344.1 Ectocondylar tuber proximodistallylong, pronounced, and extends almost to distal endof femur.
NODE H.
ALL: 234.1 Humeral torsion present; 249.1 Ulnarfacet for radius transversely expanded and con-cave; 330.1 Femoral head approximately 90 de-grees from shaft (head directed horizontally).
ACCTRAN: 22.1 Pneumatic excavation withoutfenestra in cranial portion of maxillary antorbitalfossa; 120.1 Splenial with notch for rostral margin ofinternal mandibular fenestra; 132.1 Premaxillarytooth crowns asymmetrical (strongly convex labially,relatively flattened lingually); 149.1 Cervical epipo-physes powerfully developed and prong-shaped;205.1 Paired caudal and cranial chevron bases;315.2 Pubic boot shape rounded, angle betweenshaft and caudal portion of boot acute.
DELTRAN: 334.1 Anterior trochanter present,separated from femoral head by cleft; 335.2 Anteriortrochanter of femur alariform; 346.1 Cnemial pro-cess arises out of the lateral surface of tibial shaft;350.1 Crista fibularis present, not well developed;351.1 Crista fibularis proximally placed; 376.1 Meta-tarsal III dorsal surface hourglass shaped.
NODE I.
ALL: 331.1 Femoral head transversely elongate.
17
A NEW PHYLOGENY OF THE CARNIVOROUS DINOSAURS
ACCTRAN: None.
DELTRAN: 22.1 Pneumatic excavation withoutfenestra in cranial portion of maxillary antorbitalfossa; 48.1 Postorbital ventral process broadertransversely than rostrocaudally with U-shapedcross-section; 149.1 Cervical epipophyses power-fully developed and prong-shaped; 315.2 Pubicboot shape rounded, angle between shaft and cau-dal portion of boot acute; 317.1 Pubic boot present,less than 30% as long as pubic shaft; 341.1 Extensorgroove in craniodistal region of femur shallow andnot conspicuous; 353.1 Fibula closely appressed totibia throughout main shaft; 360.1 Fibula distal endless than twice craniocaudal width at midshaft, andconsequently astragalar cup for fibula reduced.
NODE J.
ALL: 31.2 Lacrimal prominences comprised ofridge continuous with raised surface of lateral edgeof nasals; 336.2 Anterior trochanter of femur proxi-mal most point above distal margin of femoral head;355.1 Proximal region of fibular medial face slightlyconcave; 365.1 Pronounced horizontal grooveacross cranial face of astragalar condyles.
ACCTRAN: -212.0 Distal expansion of scapulabroad (subequal in width to proximal end of scap-ula); 339.1 Muscle scar in craniodistal region of fe-mur present, non-elliptical in shape.
DELTRAN: 41.1 Orbit shorter than internal antor-bital fenestra length; 61.1 Jugal recess; 64.2 Broadcontact between dorsal ramus of quadratojugal andlateroventral ramus of squamosal; 205.1 Pairedcaudal and cranial chevron bases; 215.1 Scapula-coracoid cranial margin with pronounced notch be-tween acromial process and coracoid; 261.1Articular surface between metacarpals I and II ex-tends well into diaphysis of metacarpal I.
NODE K.
ALL: 139.1 Axial "spine table" (expanded distalend of neural spine); 146.1 Ventral keel on axial cen-trum absent; 155.1 Cervical zygapophyses dis-placed laterally away from centrum in dorsal view;235.1 Humeral shaft sigmoid.
ACCTRAN: 4.1 Premaxillary symphyseal regionU-shaped in ventral view; -10.0 Premaxilla and na-sal meet subnarially; 60.2 Jugal ventral quadratoju-gal process extends further caudally than dorsalquadratojugal process; 260.1 Metacarpal I one halfto one third metacarpal II length; 264.1 MetacarpalIII very much narrower (less than 50%) than meta-carpal II; 266.1 Base of metacarpal III set on palmarsurface of hand below base of metacarpal II; 267.1Proximal articulation of metacarpal III triangular;126.1 Cranial cervicals broader than deep on cranial
surface, with kidney-shaped articular surfaces thatare taller laterally than at midline; 287.2 Anterior tro-chanter of femur proximalmost point above distalmargin of femoral head.
DELTRAN: 319.1 Pubis and ischium proximalshafts narrow.
As in GAUTHIER (1986), NOVAS (1992), HOLTZ(1994), SERENO (1997), and most other recent stud-ies of theropod phylogeny, a robustly supportedclade of birds and theropods more closely related tobirds than to Ceratosaurus was discovered. Thisclade, GAUTHIER's (1986) Tetanurae, comprises pri-marily the subdivisions Carnosauria and Coeluro-sauria, discussed below. However, there are severalforms of theropod which (in the present analysis) lieoutside the carnosaur-coelurosaur clade Avethero-poda, yet were found to share a more recent com-mon ancestor with birds than with Ceratosaurus.
The relationships among the basal tetanurines,informally referred to as "megalosaurs" (in, for ex-ample, GAUTHIER (1986): p. 10) have been problem-atic in most recent studies (HOLTZ, 1994; SERENO etal., 1994, 1996; SERENO, 1997). Unfortunately, thepresent analysis does not provide strong support forany particular scenario of "megalosaur" phylogeny.This uncertainty seems to stem from a number ofsources, the most important being: a) the fairly largenumber of missing data from some of these taxa,representing our inadequate knowledge of the os-teology of these forms at present; b) the lack of spe-cializations in many of these taxa beyond thoseshared by all tetanurines, particularly in the case ofthe non-spinosaurid "megalosaurs"; and c) alterna-tively, the highly apomorphic nature of the skulls ofspinosaurids (CHARIG & MILNER, 1997; SERENO etal., 1998), in which the rostrum, dentition, palate,and basicranium are uniquely modified amongtheropods.
As previously noted, the fragmentary taxon"Megalosaurus" hesperis falls within this sector ofthe cladogram, but no particular sister group rela-tionship was better supported than the others.
NOVAS(1992) proposed the name "Avipoda" for aclade comprised of Eustreptospondylus, Piatnitz-kysaurus, and more advanced tetanurines. This cor-responds to node I in this study. If additional work ontheropod phylogenetics continues to support a sub-group excluding some basal tetanurines but unitingEustreptospondylus, Piatnitzkysaurus, and morederived taxa, this name would serve as a useful la-bel.
SERENO et al. (1994, 1996; 1998) and SERENO(1997) presented evidence that several of these ba-sal tetanurines (in particular, Torvosaurus, Eustrep-tospondylus, and Spinosauridae) represented a
18
T.R. HOLTZ, JR.
distinct clade of theropod, exclusive of other car-nivorous dinosaurs. CHARIG & MILNER (1997) dem-onstrated that several of the "synapomorphies" forthis postulated "Torvosauroidea" (later changed to"Spinosauroidea") are absent in Spinosauridae. Inthe present study, some of the other characters sug-gested to support a monophyletic "Spinosauroidea"(13.1, 14.1, 22.1, 35.1, and 279.1) are explained inthe most parsimonious distribution of states in thisanalysis to be basal tetanurine features lost in someor all avetheropod taxa.
Of particular note are conditions related to therostral ramus ("anterior ramus" in BAKKER et al.(1992) and SERENO et al. (1994, 1996)) of the max-illa. The maxillae of basal tetanurines differ fromthose of ceratosaurs in the shape of the rostrodorsalmargin (Fig. 6). In ceratosaurs and herrerasauridsthis line is a simple curve, convex dorsally, from thedorsal ramus to the tooth line. In tetanurines primi-tively this surface is a more complex curve, with a de-pression ventral to the external naris. This producesa rostral ramus to the maxilla, rostral to the dorsal ra-mus (13.1). The presence of this structure is found inall non-avetheropods for which skull material isknown (although the condition in spinosaurids is dis-tinct from the other taxa, given their elongate snouts:CHARIG & MILNER (1997)), and is also present in theskulls of most carnosaurs (the notable absences be-ing Sinraptor and Yangchuanosaurus) and in basalcoelurosaurs for which the skull is known (Procera-tosaurus and Ornitholestes). As with sinraptorid car-nosaurs, the clade of coelurosaurs comprised ofScipionyx and Maniraptoriformes have the primitivestate with a simple dorsally convex curvature of therostral portion of the maxilla. This distribution is mostparsimoniously explained as independent reversalsin Sinraptoridae and advanced Coelurosauria.
SERENO et al. (1994, 1996) specifically recog-nized a derived condition in which the rostral ramuswas longer rostrocaudally than tall dorsoventrally. Inthe present study two different derived states wererecognized to describe the relative proportions ofthe rostral ramus: those forms for which the struc-ture is present, but shorter rostrocaudally than talldorsoventrally (14.1) and the condition recognizedby SERENO et al. (1994, 1996) (14.2). Rather thanuniting Spinosauridae, Torvosaurus, Eustrepto-spondylus, and Afrovenator outside of other thero-pods, however, this condition was found to be thestate at the base of Tetanurae, and subsequentlyshortened in various tetanurine taxa.
Curiously, all known basal tetanurines representfairly large sized taxa (approximately 6 m or longer).
NODE L.
ALL: 17.1 Maxillary fenestra; -22.0 Pneumaticexcavation without fenestra in cranial portion ofmaxillary antorbital fossa absent; 322.1 Obturatorprocess of ischium separate, trapezoidal; 323.1 Ob-turator process of ischium proximally placed; 341.2Extensor groove in craniodistal region of femur deepand conspicuous
ACCTRAN: 181.2 Presacral pleurocoels camel-late; 217.1 Ventral coracoid process well developed;355.2 Proximal region of fibular medial face well ex-cavated
DELTRAN: 58.1 Jugal participates in internal an-torbital fenestra; 197.2 Transition point in proximalhalf of tail; 253.1 Distal carpal I block does not over-lap metacarpal II dorsally, but does so ventrally;254.1 Distal carpal I fused to distal carpal II; 255.1Semilunate carpal block fully developed with trans-verse trochlea; 260.1 Metacarpal I one half to onethird metacarpal II length; -279.0 Pollex ungual lessthan three times longer than height of articular facet;-283.0 Manual ungual moderate length; 339.2 Mus-cle scar in craniodistal region of femur present, ellip-tical in shape; 364.1 Astragalar distal condylesoriented cranioventrally
NODE M. AVETHEROPODA
ALL: -35.0 Lacrimal dorsal (rostral) ramus dor-soventrally deep; -48.0 Postorbital ventral processbroader rostrocaudally than transversely; 58.1Squamosal constriction of lateral temporal fenestra;169.1 Scars for interspinous ligaments terminatebelow apex of neural spine; 208.1 Middle chevronwith dramatic bend in distal portion ("L-shaped");274.1 First phalanx of pollex greater than length ofmetacarpal II; 288.1 Iliac preacetabular fossa for M.cuppedicus
ACCTRAN: 330.2 Femoral head greater than 90degrees from shaft (head directed dorsally)
DELTRAN: 38.1 Prefrontal-frontal peg-in-socketsuture; 76.1 Palatine tetraradiate; 78.1 Palatine re-cesses; 120.1 Splenial with notch for rostral marginof internal mandibular fenestra; 123.1 Retroarticularprocess of articular faces caudally; 132.1 Premaxil-lary tooth crowns asymmetrical (strongly convex la-bially, relatively flattened lingually); 212.1 Distalexpansion of scapula reduced or absent; 217.1 Ven-tral coracoid process well developed; 225.1 Furcula;233.1 Manus/(humerus + radius) length ratiogreater than 66%; -249.0 Ulnar facet for radius smalland flat; 264.1 Metacarpal III very much narrower(less than 50%) than metacarpal II; 266.1 Base ofmetacarpal III set on palmar surface of hand belowbase of metacarpal II; 267.1 Proximal articulation ofmetacarpal III triangular; 268.1 Metacarpal IV lessthan half length of metacarpal II; 278.1 Pollex larger
19
A NEW PHYLOGENY OF THE CARNIVOROUS DINOSAURS
than other manual unguals; 355.2 Proximal region offibular medial face well excavated
As in NOVAS (1992), HOLTZ (1994), SERENO et al.(1994, 1996), and SERENO (1997), a clade was rec-ognized containing Allosaurus and those taxa clos-est to it as one branch, and Aves and those taxaclosest to it as the other, outside of the more primitivetetanurines. Following HOLTZ (1994), and using aname for this clade first published in PAUL (1988),this clade comprised of all descendants of the mostrecent common ancestor of Allosaurus and Neorni-thes is termed Avetheropoda. SERENO et al. (1994,1996) and SERENO (1997, 1998) suggested the al-ternative name "Neotetanurae": indeed, SERENO(1997, 1998) uses the same definition as the above,rendering this term a junior objective synonym ofAvetheropoda (see also PADIAN, HUTCHINSON &HOLTZ (1999)). Perhaps the name "Neotetanurae"might be preserved as the name for a more inclusivetaxon (for example, Neornithes and all taxa sharinga more recent common ancestor with Neornithesthan with Spinosauridae).
The Early Cretaceous (?Barremian) Afrovenatorabakensis was found to share several derived char-acters with Avetheropoda lacking in other basal teta-nurines: in particular, unquestionable presence of amaxillary fenestra (17.1) and an obturator processon the ischium (322.1, 323.1). Additionally, the semi-lunate carpal block (255.1) is present in Afrovenatoras it is in avetheropods, but as the carpus is un-known in other non-avetheropod tetanurines, this
derived feature may be synapomorphic for a moreinclusive group (see Discussion below).
The two divisions of Avetheropoda are termedCarnosauria (Allosaurus and all taxa sharing a morerecent common ancestor with Allosaurus than withNeornithes) and Coelurosauria (Neornithes and alltaxa sharing a more recent common ancestor withNeornithes than with Allosaurus): see PADIAN,HUTCHINSON & HOLTZ (1999) for discussion of thehistory of these terms. Both carnosaurs and coeluro-saurs share the derived character state of fusedclavicles (furculae): however, the lack of preserva-tion of clavicles in more basal tetanurines allows forthe possibility of this character state being synapo-morphic for an even more inclusive group (see Dis-cussion below). Twenty four other derived characterstates unite carnosaurs and coelurosaurs to the ex-clusion of other theropod clades, but sixteen ofthese cannot be fairly assessed at present in basaltetanurines, as the skeletal elements concerned arenot recovered for these taxa at present.
NODE N. CARNOSAURIA
ALL: 23.1 Lateral surface of nasal participates inantorbital cavity, forming a nasal antorbital fossa;29.1 Nasal recesses; 75.1 Palatines meet medially;83.1 Nuchal crest pronounced; 97.1 Distanceacross basal tubera less than the transverse width ofoccipital condyle; 100.1 Basipterygoid processesshort, but not fused to pterygoids; 166.1 Ventral pro-
20
T.R. HOLTZ, JR.
Fig. 6 - Cladogram comparing the left maxillae (in left lateral view) of the ceratosaur Dilophosaurus (modified fromWELLES, 1984), the basal tetanurine Afrovenator (modified from SERENO et al., 1994), and the avetheropod carnosaurMonolophosaurus (modified from ZHAO& CURRIE, 1993). Arrow indicates the presence of the rostral ramus of the maxilla,a tetanurine synapomorphy (character 13.1). Not to scale.
cesses (hypapophyses) on cervicodorsal vertebraepresent as small protrusions.
ACCTRAN: 67.2 Quadrate foramen small andenclosed within dorsal ramus of quadrate; 113.1Rostral surangular foramen large, in rostrally-oriented depression; 229.1 Humerus/scapulalength ratio less than 65%; 314.1 Pubic foramen per-forating pubic apron in distal half of shaft; 350.2Crista fibularis well developed; 382.1 Pedal digit Iphalanges 1+2 subequal to pedal digit III phalanx 1.
DELTRAN: 24.1 Nasal participates in antorbitalcavity; 60.2 Jugal ventral quadratojugal process ex-tends further caudally than dorsal quadratojugalprocess; 70.1 Quadrate articulation projects wellcaudal to the caudalmost point of the occipital con-dyle.
NODE O. ALLOSAUROIDEA
ALL: 21.1 Pneumatic excavation of the ascend-ing ramus of the maxilla; 26.2 Narial prominencescomprised of paired ridges along lateral edges ofnasals; 33.1 Lacrimal recess, single opening pres-ent; 47.1 Postorbital prominences present; 69.1Quadrate articulation projects well ventral of theventral surface of the maxilla; 116.2 Horizontal shelfon lateral surface of surangular, rostral and ventralto the mandibular condyle, prominent and pendant;179.1 Caudal dorsal neural spines oriented crani-ally; 315.4 Pubic boot shape triangular (apex cau-dal) in ventral view and angle between shaft andcaudal portion of boot acute.
ACCTRAN: 118.1 External mandibular fenestrareduced; 175.1 Dorsal centrum "hourglass" shaped,central section depth less than 60% height of cranialface; 307.1 Obturator foramen of pubis open ven-trally to form obturator notch.
DELTRAN: 4.1 Premaxillary symphyseal regionU-shaped in ventral view; 67.2 Quadrate foramensmall and enclosed within dorsal ramus of quadrate;77.1 Jugal process of palatine expanded; 81.1 Ven-tral ectopterygoid recess present and comma-shaped; 181.2 Presacral pleurocoels camellate;257.2 Metacarpal IV present, without phalanges;314.1 Pubic foramen perforating pubic apron in dis-tal half of shaft; 316.1 Caudal portion of pubic bootlonger than cranial portion, but latter present; 350.2Crista fibularis well developed; 382.1 Pedal digit Iphalanges 1+2 subequal to pedal digit III phalanx 1.
NODE P. SINRAPTORIDAE
ALL: 9.1 External nares with marked inset of thecaudal margin; -13.0 Rostral ramus of maxilla ab-sent, rostrodorsal surface of maxilla forms convexsurface from dorsal ramus to ventral margin; 20.1Promaxillary fenestra larger than maxillary fenestra;
56.1 Squamosal flange covering quadrate head inlateral view; 167.1 Neural spines of dorsals equal totwice centrum height; 357.1 Cranial protuberanceon fibula below expansion.
ACCTRAN: -57.0 Squamosal does not constrictlateral temporal fenestra.
DELTRAN: -10.0 Premaxilla and nasal meetsubnarially; -14.0 Rostral ramus absent; 113.1 Ros-tral surangular foramen large, in rostrally-orienteddepression; 175.1 Dorsal centrum "hourglass"shaped, central section thickness less than 60%height of cranial face; -330.1 Femoral head approxi-mately 90 degrees from shaft (head directed hori-zontally).
NODE Q. ALLOSAURIDAE
ALL: -58.0 Jugal does not participate in internalantorbital fenestra; 103.1 Occipital condyle con-stricted neck; 115.1 Rostral ramus of surangulardeep; 178.1 Dorsal column subequal to femurlength; 257.3 Metacarpal IV absent; 317.2 Pubicboot present, greater than 30% as long as pubicshaft; 318.1 Pubic-ischial contact only narrow re-gion; 349.1 Lateroproximal condyle of tibia with con-spicuous waisting between body of condyle andmain body of tibia in proximal view.
ACCTRAN: 16.2 Promaxillary fenestra present,obscured in lateral view by ascending ramus of max-illa; 87.2 Paroccipital process curving ventrally andpendant; 112.1 Dentary caudal depth 150-200%depth of dentary symphysis; -170.0 Apices of dorsalneural spines unexpanded; 214.1 Caudal margin ofacromial process of scapula forms abrupt change,perpendicular to blade.
DELTRAN: -113.0 Rostral surangular foramenabsent or very small pit; 118.1 External mandibularfenestra reduced; 229.1 Humerus/scapula lengthratio less than 65%; 307.1 Obturator foramen of pu-bis open ventrally to form obturator notch; 330.2Femoral head greater than 90 degrees from shaft(head directed dorsally).
NODE R.
ALL: 3.2 Five premaxillary teeth; 199.1 Distalcaudal vertebrae with moderate interlocking, prezy-gapophyses extend more than one half, but lessthan one, centrum length; -212.0 Distal expansion ofscapula broad, subequal in width to proximal end.
DELTRAN: 10.1 Premaxilla and nasal do notmeet subnarially; 87.2 Paroccipital process curving
21
A NEW PHYLOGENY OF THE CARNIVOROUS DINOSAURS
ventrally and pendant; -169.0 Scars for interspinousligaments terminate at apex of neural spine; 214.1Caudal margin of acromial process of scapula formsabrupt change, perpendicular to blade.
NODE S
ALL: 36.1 Lacrimal suborbital bar; 41.1 Frontal-frontal suture fused; 50.1 Postorbital-lacrimal con-tact broad; 53.1 Postorbital suborbital flange; -100.0Basipterygoid processes moderately long; 159.1Elevation of cranial face of midcervical centra; 191.1Caudal pleurocoels present in centra.
ACCTRAN: -166.0 Ventral processes (hypapo-physes) on cervicodorsal vertebrae absent; 183.1Sacral pleurocoels; 236.1 Humeral head offset andemarginated ventrally by groove; 241.1 Deltapecto-ral crest on humerus expanded and offset from hu-meral shaft.
DELTRAN: -14.1 Rostral ramus of maxillashorter rostrocaudally than dorsoventrally.
NODE T.
ALL: -10.0 Premaxilla and nasal meet subnari-ally; 15.2 Maxillary antorbital fossa greatly reducedin size, not extending much beyond rim of the exter-nal antorbital fossa; -21.0 Pneumatic excavation ofascending ramus of maxilla absent; 26.3 Narialprominences knobby rugosities across dorsal andlateral surface of nasals, extending onto dorsalmostsurface of maxillae; 52.1 Postorbital bulbous ros-trally projecting rugosity; 88.1 Basisphenoid, but notparasphenoid rostrum, strongly expanded andpneumatized; 131.1 Lateral surface of teeth withwrinkles in enamel internal to serrations.
ACCTRAN: 5.1 Premaxilla subnarially verydeep, main body taller dorsoventrally than long ros-trocaudally; 8.1 Maxillary process of premaxilla re-duced, maxilla participates broadly in ventralsurface of external naris; -17.0 Maxillary fenestraabsent; 37.1 Prefrontals reduced or absent; 42.2Frontal-parietal suture on dorsal surface of skullfused, suture indistinguishable; -57.0 Squamosaldoes not constrict lateral temporal fenestra; -60.0Jugal dorsal and ventral quadratojugal processessubequal in caudalmost extension; 62.1 Jugal re-cesses; 68.1 Quadrate dorsal ramus height greaterthan height of orbit; 105.1 Dentary end squared withexpanded tip; 157.1 Cranial cervicals broader thandeep on cranial surface, with reniform (kidney-shaped) articular surfaces that are taller laterallythan at midline.
DELTRAN: -87.0 Paroccipital process orientedmore caudally than dorsally.
As argued by PADIAN, HUTCHINSON & HOLTZ(1999) (see also HOLTZ & BRETT-SURMAN, 1997),
the long established name Carnosauria HUENE,1920 may be conserved as the clade comprised ofAllosaurus and all taxa sharing a more recent com-mon ancestor with this taxon than with Neornithes.In the present study, the oldest and most basal formin this clade is the Middle Jurassic Monolophosau-rus jiangi ZHAO & CURRIE, 1993 of China. However,SERENO et al. (1994, 1996) and SERENO (1997)have proposed that Cryolophosaurus ellioti HAM-MER & HICKERSON, 1994 is a member of this clade. Ifthis hypothesis is correct, the age of this form wouldindicate not only a minimum Early Jurassic date forthe origin of Carnosauria but also of the Coelurosau-ria (see also discussion of maniraptoriforms below),as well as such an early date for the origin of each ofthe various basal tetanurine lineages.
HARRIS (1998) observed that palatines that meetmedially are present in both Sinraptor and Allosau-rus. Such a geometry appears to be present inMonolophosaurus (ZHAO & CURRIE, 1993), but isabsent in basal sauropodomorphs, Herrerasaurus,ceratosaurs, tyrannosaurids, ornithomimids, dro-maeosaurids, and other coelurosaurs. In these taxa,the palatines remain separated medially by the ros-tral processes of the pterygoids.
Allosauroidea CURRIE & ZHAO, 1993a has beenproposed as the name for the clade comprised of alldescendants of the most recent common ancestorof Allosaurus and Sinraptor (see also PADIAN,HUTCHINSON & HOLTZ, 1999). (SERENO (1997,1998) uses the same name but with the definitionemployed here for Carnosauria). In the presentstudy, this clade would contain all carnosaurs exceptfor Monolophosaurus. HARRIS (1998) observed thatallosauroids were characterized by caudal dorsalvertebrae in which the neural spines were orientedcranially rather than vertically (as in other thero-pods). This orientation is not present in Monolopho-saurus, but is found in Sinraptor, Allosaurus, andAcrocanthosaurus. As such, it is supported here asa synapomorphy of Allosauroidea.
Within the allosauroids, a sister group relation-ship for Sinraptor and Yangchuanosaurus, pro-posed in the first study of the former taxon (CURRIE &ZHAO, 1993a), is supported here. Similarly, HUTT,MARTILL & BARKER (1996) suggested that theirnewly described Neovenator (of the Wealden Groupof the Isle of Wight) was closely related to the LateJurassic North American genus Allosaurus, a posi-tion also retained in the present analysis.
The union of Acrocanthosaurus, Giganotosau-rus, and Carcharodontosaurus, first proposed (witha different topology) by SERENO et al. (1996) wasfound in the present analysis. This clade of giganticmid-Cretaceous (Aptian-Cenomanian) carnosaurswas called "Carcharodontosauridae" by SERENO et
22
T.R. HOLTZ, JR.
al. (1996), although (under the phylogenetic taxon-omy used here) this clade is part of Allosauridae(i.e., Allosaurus and all taxa sharing a more recentcommon ancestor with Allosaurus than with Sinrap-tor). Although the analysis of CURRIE & CARPENTER(in press) found that Acrocanthosaurus was moreclosely related to Allosaurus than to Giganotosau-rus or Carcharodontosaurus, this study agrees withSERENO et al. (1996) and HARRIS (1998) in groupingthe three giant mid-Cretaceous taxa exclusive of theLate Jurassic Allosaurus.
Examining the character states at node T revealsmany derived features also demonstrated by abeli-sauroids. Indeed NOVAS (1997c) has suggested thatGiganotosaurus and Carcharodontosaurus areclosely related to the abelisauroid neoceratosaurs,a very different phylogenetic position from thatfound here. Although there are several cranial syna-pomorphies potentially uniting Carcharodontosau-rus and Abelisauridae (in general) or Abelisaurus (inparticular), additional features unite the African di-nosaur with Giganotosaurus, while further cranialand postcranial character states group this SouthAmerican dinosaur with the unquestioned teta-nurine Acrocanthosaurus (see also the Discussionbelow).
In the current phylogeny, Carcharodontosaurus(of Cenomanian age) is the latest known carnosaur.No fossil evidence presently known indicates thesurvival of Carnosauria into the last twenty eight mil-lion years of the Cretaceous.
NODE U. COELUROSAURIA
ALL: -147.0 Cervical centra surfaces amphiplat-yan; 315.3 Pubic boot boat-shaped (pointed crani-ally and caudally) in ventral view and angle betweenshaft and caudal portion of boot acute; 354.1 Fibulaproximal end 75% or more proximal width of tibia.
ACCTRAN: 15.1 Maxillary antorbital fossagreater than 40% of the rostrocaudal length of theantorbital cavity; -31.0 Lacrimal prominences ab-sent; -45.0 Orbit shape round; -54.0 Postorbital fron-tal process sharply upturned; 60.1 Jugal dorsalquadratojugal process extends further caudally thanventral quadratojugal process; -61.0 Jugal recessesabsent; 70.2 Quadrate articulation rostral to caudal-most point of occipital condyle; 80.1 Subsidiary fen-estra between pterygoid and palatine; 82.1Endocranial cavity enlarged relative to other dino-saurs, but temporal musculature extends onto fron-tals; 86.1 Paroccipital process with hollow proximalportion; 88.1 Basisphenoid, but not parasphenoidrostrum, strongly expanded and pneumatized; 90.1Three tympanic recesses; 91.1 Branches of internalcarotid artery enter hypoglosseal fossa through sin-gle common foramen; 115.1 Rostral ramus of suran-
gular deep; 121.1 Coronoid extremely reduced orabsent; 153.1 Cervical prezygapophyses flexed;157.1 Cranial cervicals broader than deep on cranialsurface, with kidney-shaped articular surfaces thatare taller laterally than at midline; -160.0 Midcervicalcentra length about twice diameter of cranial face;190.1 Number of caudals between 30 and 44; 196.1Caudal transverse processes only on caudals I-XVor fewer; 209.1 Distal chevrons with cranial and cau-dal projections, and more than twice as long cranio-caudally as tall dorsoventrally ("boat-shaped"); -215.0 Scapulacoracoid cranial margin smooth;226.1 Forelimb (humerus+radius+manus)/hindlimb(femur+tibia+pes) length ratio greater than 50% butless than 120%; 227.1 Forelimb/presacral vertebralseries length ratio greater than 75% but much lessthan 200%; 232.2 Radius/humerus length ratiogreater than 76%; 245.1 Ulnar shaft bowed cau-dally; 272.1 Length of phalanx 3 of manual digitIII/(sum of lengths of phalanges 1+2 of digit III)greater than 100%; 330.2 Femoral head greaterthan 90 degrees from shaft (head directed dorsally);332.1 Greater trochanter cleft from femoral head;347.1 Incisura tibialis cranialis occupies more than66% of medial surface of proximal tibia; 362.2 Astra-galar ascending process craniocaudally reducedand proximodistally tall, with dorsal margin sigmoid("ornithomimoid/albertosauroid condition"); -365.0No pronounced horizontal groove across cranialface of astragalar condyles; 380.1 Metatarsal I plan-tar to medial side of metatarsal II; 386.1 Pedal un-gual II significantly longer than pedal ungual III.
DELTRAN: None.
NODE V.
ALL: None
ACCTRAN: 307.1 Obturator foramen of pubisopen ventrally to form obturator notch; 322.2 Obtu-rator process of ischium separate, triangularshaped; -341.1 Extensor groove in craniodistal re-gion of femur present, but shallow and not conspicu-ous; 349.1 Lateroproximal condyle of tibia withconspicuous waisting between body of condyle andmain body of tibia in proximal view.
DELTRAN: 4.1 Premaxillary symphyseal U-shaped in ventral view; -10.0 Premaxilla and nasalmeet subnarially; 15.1 Maxillary antorbital fossagreater than 40% of the rostrocaudal length of theantorbital cavity; -45.0 Orbit shape round; -61.0 Ju-gal recesses absent; 70.2 Quadrate articulation ros-tral to caudalmost point of occipital condyle.
NODE W.
ALL: None.
ACCTRAN: 7.1 Medial alae from premaxillaemeet in front of vomera; -44.0 Orbit longer than inter-
23
A NEW PHYLOGENY OF THE CARNIVOROUS DINOSAURS
nal antorbital fenestra length; 116.1 Horizontal shelfon lateral surface of surangular, rostral and ventralto the mandibular condyle, prominent and extendslaterally.
DELTRAN: 307.1 Obturator foramen of pubisopen ventrally to form obturator notch; 318.1 Pubic-ischial contact only narrow region; 337.1 Fourth tro-chanter of femur little developed; -341.1 Extensorgroove in craniodistal region of femur present, butshallow and not conspicuous; 349.1 Lateroproximalcondyle of tibia with conspicuous waisting betweenbody of condyle and main body of tibia in proximalview; 362.2 Astragalar ascending process cranio-caudally reduced and proximodistally tall, with dor-sal margin sigmoid ("ornithomimoid/albertosauroidcondition"); -365.0 No pronounced horizontalgroove across cranial face of astragalar condyles.
NODE X.
ALL: 333.1 Femoral head transversely elongate.
ACCTRAN: 60.1 Jugal dorsal quadratojugal pro-cess extends further caudally than ventral quadrato-jugal process; 81.2 Ventral ectopterygoid recesspresent and subcircular; 277.1 Manual ungual re-gion palmar to ungual groove subequal in width toregion dorsal to ungual groove; 282.1 Manual un-gual cross section blade-like, more than three timesas deep as wide; 357.1 Cranial protuberance on fib-ula below expansion.
DELTRAN: -31.0 Lacrimal prominences absent;-44.0 Orbit longer than internal antorbital fenestralength; 82.1 Endocranial cavity enlarged relative toother dinosaurs, but temporal musculature extendsonto frontals; 115.1 Rostral ramus of surangulardeep; -160.0 Midcervical centra length about twicediameter of cranial face; 181.2 Presacral pleuro-coels camellate; 190.1 Number of caudals between30 and 44; 196.1 Caudal transverse processes onlyon caudals I-XV or fewer; 209.1 Distal chevrons withcranial and caudal projections, and more than twiceas long craniocaudally as tall dorsoventrally ("boat-shaped"); 227.1 Forelimb/presacral vertebral serieslength ratio greater than 75% but much less than200%; 322.2 Obturator process of ischium sepa-rate, triangular shaped; 332.1 Greater trochanter offemur cleft from femoral head.
ACCTRAN: -13.0, -14.0 Rostral ramus of maxillaabsent, rostrodorsal surface of maxilla forms con-vex surface from dorsal ramus to ventral margin; -
26.0 Narial prominences absent; 71.1 Quadratepneumaticity well developed; 72.1 Secondary pal-ate well ossified from premaxilla through one-halfthe length of the ventral surface of the maxilla; 103.1Occipital condyle constricted neck; 114.1 Caudalsurangular foramen large opening; 369.1 Metatar-sus proportions elongate relative to most othertheropods of same femur length; -376.0 MetatarsalIII dorsal surface shape elliptical.
DELTRAN: 263.1 Metacarpal III clearly shorterthan metacarpal II; 272.1 Length of phalanx 3 ofmanual digit III/(sum of lengths of phalanges 1 + 2 ofdigit III) greater than 100%; 277.1 Manual ungualpalmar and dorsal regions subequal in width; 282.1Manual ungual cross section blade-like, more thanthree times as deep as wide.
NODE Z.
ALL: -235.0 Humeral shaft straight; 257.3 Meta-carpal IV absent.
ACCTRAN: 157.1 Cranial cervicals broader thandeep on cranial surface, with reniform (kidney-shaped) articular surfaces that are taller laterallythan at midline.
DELTRAN: -13.0, -14.0 Rostral ramus of maxillaabsent, rostrodorsal surface of maxilla forms con-vex surface from dorsal ramus to ventral margin; -26.0 Narial prominences absent; 153.1 Cervicalprezygapophyses flexed; -215.0 Scapulacoracoidcranial margin smooth; -221.0 Sternal plates un-fused; -222.0 Sternum carina absent; -245.0 Ulnarshaft bowed caudally.
ACCTRAN: 8.1 Maxillary process of premaxillareduced, maxilla participates broadly in ventral sur-face of external naris; 37.1 Prefrontals reduced orabsent; 118.1 External mandibular fenestra re-duced; 158.1 Cranial cervical centra extend beyondcaudal extend of neural arch; 168.1 Apices of dorsalneural spines expanded transversely to form "spinetable"; 188.1 Sacral neural spines fuse to form lam-ina; -240.0 Humeral ends little or not expanded;284.2 Manual unguals straight.
Coelurosauria is a well-supported clade of teta-nurine dinosaurs. Most of the traditional coeluro-saurs of previous studies (GAUTHIER, 1986; HOLTZ,1994; SERENO, 1997; SUES, 1997), known from rela-tively complete material, comprise a clade of derivedforms, the Maniraptoriformes HOLTZ, 1996b: these
24
T.R. HOLTZ, JR.
taxa are discussed below. As in the case of basalTetanurae, however, there exist a number of frag-mentary forms which demonstrate some shared de-rived characters with Maniraptoriformes comparedto other theropods, but which were found to lie out-side that clade..
Among these, Proceratosaurus bradleyi is theoldest currently known (Bathonian age, Middle Ju-rassic). An alleged therizinosauroid maniraptori-form from the Sinemurian age (Early Jurassic) of theLower Lufeng Formation, Yunnan, China (ZHAO &XU, 1998) is even older. If substantiated, this wouldindicate that Maniraptoriformes (and indeed, thevarious lineages of the oviraptorosaur-Microvenatorclade, Paraves, Compsognathidae, and Arctometa-tarsalia, the ancestors of the basal coelurosaurs,and Carnosauria) would date back to at least the Si-nemurian. However, the specimen in question is anisolated dentary, and given the resemblance of thedentary of therizinosauroids and basal sauropodo-morphs (the latter common to the Early Jurassic di-nosaurian fauna), this intriguing discovery isgreeted with some caution.
Regardless of the phylogenetic identity of theYunnan specimen, Proceratosaurus sharesuniquely with other coelurosaurs several derivedcharacteristics. The maxillary antorbital fossa (thewall of bone on the rostral portion of the antorbitalfenestra: WITMER, 1997) forms 40% of the total ros-trocaudal length of the antorbital fenestra, a derivedcondition first hypothesized as a coelurosauriansynapomorphy by SERENO et al. (1994, 1996) andsupported here (Fig. 7). In carnosaurs, basal teta-nurines, and ceratosaurs, the maxillary antorbitalfossa represents a much smaller fraction of thislength (and, correspondingly, the internal antorbitalfenestra represents a larger fraction of the totalstructure). Furthermore, the articulation betweenthe quadrates and the mandible lie rostral to the cau-dalmost point of the occipital condyle in Procerato-saurus and most other coelurosaurs. In contrast, thequadrate articulation lies at the same point or rostralto the caudalmost point of the occipital condyle inceratosaurs, basal tetanurines, and carnosaurs.Even in the largest skulled of coelurosaurs, large ty-rannosaurids such as Tyrannosaurus rex (MOLNAR,1991) the articulation of the quadrates is slightly ros-tral to the end of the occipital condyle. Coupled withthe flexion of the cervical prezygapophyses and thedevelopment of kidney-shaped articular surfaces inthe cranial cervicals, the forward placement of themandibular joint may indicate specializations to-wards greater lateral mobility in the necks of coelu-rosaurs relative to other theropods. In othertheropods, the posterior placement of the mandibu-lar joint may have interfered with lateral motion of the
neck. Unfortunately, the cervicals of Proceratosau-rus are presently unknown.
The inclusion of Gasosaurus constructus in Coe-lurosauria is novel to this study. This poorly knownMiddle Jurassic Chinese form is admittedly frag-mentary. Its pelvis retains several primitive featurestransformed in other, later coelurosaurs: the obtura-tor foramen is present, the ischium is footed, and theobturator process appears to be trapezoidal. Never-theless, the hindlimb possesses several coeluro-saur characteristics: a femoral head at an anglegreater than 90 degrees to the femoral shaft; alesser trochanter cleft from the femoral head, and afibula whose proximal portion is greater than 75%the proximal width of the tibia. Given the incompletenature of this taxon, additional character evidencemay reveal it does not belong to Coelurosauria.Pending such discovery, however, the current analy-sis suggests that this form does indeed share a morerecent common ancestor with birds than with Allo-saurus. (P. Currie, pers. comm. 1998, indicates thatas yet undescribed specimens suggest that Gaso-saurus is in fact a primitive carnosaur, perhaps a sin-raptorid).
The Late Cretaceous (Campanian) North Ameri-can taxon Dryptosaurus, previously suggested to bea coelurosaur by DENTON (1990), was found to bemore derived than Gasosaurus in that it possesses atrue obturator notch, a narrow proximal contact be-tween the pubis and ischium, and a few otherhindlimb characters. Unfortunately, this taxon too isincompletely known at present.
The Late Jurassic Ornitholestes hermanni OS-BORN, 1903 is one of the most completely known ba-sal coelurosaurs. As in HOLTZ (1994), SERENO et al.(1996), and SERENO (1998), but unlike GAUTHIER(1986) and MAKOVICKY & SUES (1998), this formwas found to be more distantly related to birds thanis Ornithomimosauria.
Sympatric with Ornitholestes, Coelurus agilisMARSH, 1879b was found to be somewhat moreclosely related to birds than the former taxon, as inMAKOVICKY & SUES (1998); however, unlike thatstudy, Coelurus was here found to lie outside theclade comprised of all descendants of the most re-cent common ancestor of birds and ornithomimo-saurs. Note that as in MAKOVICKY & SUES (1998),this study follows MILES, CARPENTER & CLOWARD(1998) in assigning the manual material AMNH 587to Coelurus rather than Ornitholestes. New, morecomplete material of Coelurus currently under studyby those latter authors will greatly aid our under-standing of this coelurosaur and its phylogenetic po-sition. Yet another small coelurosaur from the LateJurassic Morrison Formation, known only from iso-
25
A NEW PHYLOGENY OF THE CARNIVOROUS DINOSAURS
lated vertebrae, was reported by MAKOVICKY(1997).
Scipionyx samniticus DAL SASSO & SIGNORE,1998 is a recently described theropod taxon from theAlbian of Italy. It is known from one of the most com-plete skeletons of any basal coelurosaur. The de-scribers considered it to be a maniraptoriform ofuncertain relationship. In the present analysis it wasfound to lie outside of Maniraptoriformes proper.However, as this specimen is likely a hatchling, itmay be that an adult individual of Scipionyx maydemonstrate maniraptoriform synapomorphies. Atpresent, this taxon is potentially of great importancein determining the character distribution in basalmembers of the maniraptoriform clade.
It should be noted that, given the often markeddifference between hatchling and adult dinosaurbody size (CARPENTER, HIRSCH & HORNER, 1994),the small size of the type and only known specimenof Scipionyx (237 mm from tip of the premaxilla to theninth caudal vertebra: DAL SASSO & SIGNORE, 1998)may not necessarily reflect a small adult size for thistaxon.
Bagaraatan ostromi OSMÓLSKA, 1996 is knownonly from a fragmentary skeleton from the NemegtFormation (Late Cretaceous, ?early Maastrichtianage) of Mongolia. In the present study its most parsi-
monious position is as the sister taxon of Manirapto-riformes. Like many maniraptoriform groups, thistaxon demonstrates a greatly enlargement of thecaudal surangular foramen (previously thought toalso occur in the carnosaur Acrocanthosaurus (seeSTOVALL & LANGSTON, 1950; HOLTZ, 1994; new evi-dence demonstrates this condition is lacking in thatcarnosaur: CURRIE & CARPENTER, in press). Baga-raatan is noteworthy for sharing many features ofthe tibia and tarsus with ceratosaurian dinosaursand with advanced ornithothoracine birds: these arebest explained here by convergence.
NODE bb. MANIRAPTORIFORMES
ALL: 313.1 Pubic apron limited to distal half of pu-bic shaft; 336.3 Anterior trochanter of femur proxi-malmost point above proximal margin of femoralhead.
ACCTRAN: None.
DELTRAN: 8.1 Maxillary process of premaxillareduced, maxilla participates broadly in ventral sur-face of external naris; -24.0 Nasal excluded from an-torbital cavity; 71.1 Quadrate pneumaticity welldeveloped; 80.1 Subsidiary fenestra between ptery-goid and palatine; 76.1 Paroccipital process withhollow proximal portion; 90.1 Three tympanic re-cesses; 118.1 External mandibular fenestra re-
26
T.R. HOLTZ, JR.
Fig. 7 - Cladogram comparing skulls (in right lateral view)of the carnosaur Allosaurus (modified from CURRIE, 1997),the basal coelurosaur Proceratosaurus (BMNH R4860, new reconstruction based on a photograph by the author), andthe tyrannosaurid Daspletosaurus (modifed from RUSSELL, 1970). Bar above skulls represent total length of antorbitalfenestra; solid portion of bar and number above represents percentage of antorbital fenestra occupied by maxillary antor-bital fossa (character 15). Not to scale.
duced; 284.2 Manual unguals extremely curved;347.1 Incisura tibialis occupies more than 66% ofmedial surface of proximal tibia; ; -376.0 MetatarsalIII dorsal surface shape elliptical; 380.1 Metatarsal Iplantar to medial side of metatarsal II.
Following HOLTZ (1996b), the clade comprised ofall descendants of the most recent common ances-tor of Ornithomimus and Neornithes is named Mani-raptoriformes. As well as ornithomimids and birds,HOLTZ (1994), SERENO (1997, 1998), and this studyagree that Maniraptoriformes also includes tyranno-saurids, troodontids, therizinosauroids, oviraptoro-saurs , and dromaeosaur ids (a l though thearrangement of these taxa differ among these stud-ies). In MAKOVICKY & SUES (1998), all of the aboveexcept for tyrannosaurids were included within thisclade (there unnamed), as were Ornitholestes andCoelurus. HOLTZ (1996b) also clarified the phyloge-netic definitions of the two main branches of mani-raptoriform coelurosaurs: Maniraptora GAUTHIER1986, Neornithes and all taxa sharing a more recentcommon ancestor with neornithines than with Or-nithomimus; and its sister taxon by definition, Arcto-metatarsalia HOLTZ, 1994, Ornithomimus and alltaxa sharing a more recent common ancestor withOrnithomimus than with Neornithes. Of note, noth-ing in these phylogenetic taxonomic definitions ne-cessitates the presence of a particular derivedcharacter or suite of characters (e.g., graspinghands and pinched metatarsi, respectively) nor aparticular combination of taxa. Instead, they simplydescribe two complimentary clades within the largertaxon Maniraptoriformes. As discussed below,some taxa with "maniraptor" hands may lie withinArctometatarsalia in the present analysis, whileother taxa with arctometatarsi are found to be mem-bers of Maniraptora. See HOLTZ (1996b) and PA-DIAN, HUTCHINSON & HOLTZ(1999) for discussion.
A character complex of interesting distribution isthe presence of a large ossified secondary palateformed by medial extensions of the maxillae (72.1)and by medial alae of the premaxillae contactingrostral to the vomers (7.1). Because the palate ofseveral coelurosaurian taxa is unknown or unpre-pared, the precise distribution of these characterstates is unknown. Nevertheless, while therizino-sauroids, oviraptorosaurs, dromaeosaurids, aviali-a n s , t y r a n n o s a u r i d s , t r o o d o n t i d s , a n dornithomimosaurs demonstrably possess thesefeatures, herrerasaurids, ceratosaurs, basal teta-nurines, and carnosaurs do not. This pattern is com-plicated by the lack of a maxillary component to thesecondary palate in Compsognathidae (Sino-sauropteryx, pers. observation 1998). An ossifiedsecondary palate has been demonstrated to be bio-mechanically advantageous in resisting torsionalforces in the skull (BUSBEY, 1995), which would be
consistent with the greater lateral flexibility possiblein the cervical region of coelurosaurs compared toother theropods (see above). Additionally (and notmutually exclusive to torsional resistance), a largeossified secondary palate might allow continuedbreathing while the rostrum was occupied with foodmanipulation and processing.
In the most parsimonious trees in this analysis allbut one of the maniraptoriform taxa unambiguouslygroup as either arctometatarsalians or as manirap-torans. However, Troodontidae is equally parsimo-niously placed as a paravian maniraptoran (thesister taxon to the dromaeosaurid-bird clade) or as abullatosaurian arctometatarsalian (the sister taxonto Ornithomimosauria). The summary cladogram(Fig. 5) follows the first of these options, but charac-ter evidence for the second are discussed below.Furthermore, it requires only one additional evolu-tionary step to move Troodontidae to a sister groupposition to the oviraptorosaur-therizinosauroidclade within Maniraptora (see Discussion).
NODE cc. ARCTOMETATARSALIA
ALL: 25.1 Nasals narrow caudally behind exter-nal nares; 39.1 Rostral portion of frontals relativelytriangular, suture with nasals forms a distinct acuteangle; 55.1 Squamosal recess; 95.1 Three cranialnerve openings in acoustic fossa; 198.1 Midcaudalvertebrae with moderately long prezygapophyses,extending more than one half but less than one cen-trum length; 199.1 Distal caudal vertebrae with mod-erate interlocking, prezygapophyses extend morethan one half, but less than one, centrum length;206.1 Bridge of bone dorsal to haemal canal in distalchevrons; -278.0 Pollex ungual subequal to ungualsof digits II and III in size; 282.2 Manual ungual cross-section subtriangular, as wide or wider than deep;287.1 Iliac blades dorsal surface meet along mid-line; 294.1 Preacetabular process of ilium cranialmargin notched; 326.1 Semicircular scar on caudalsurface of ischium, just distal to iliac process; 341.2Extensor groove in craniodistal region of femur deepand conspicuous; 350.2 Crista fibularis well devel-oped; 373.1 Metatarsals II and IV contact at mid-shaft on the plantar surface; 375.2 Metatarsal IIIdorsal surface area clearly smaller than metatarsalsII and IV; 377.1 Arctometatarsus.
ACCTRAN: 251.1 Distal carpal shape flat anddiscoidal, no distinct articular surfaces; 283.2 Man-ual unguals relatively short; 363.1 Round externalfossa at base of ascending process of astragalus;379.2 Metatarsal I placed distally.
DELTRAN: 7.1 Medial alae from premaxillaemeet in front of vomera; 60.1 Jugal quadratojugaldorsal process extends further caudally then ventralquadratojugal process; 72.1 Secondary palate well
27
A NEW PHYLOGENY OF THE CARNIVOROUS DINOSAURS
ossified from premaxilla through one-half the lengthof the ventral surface of the maxilla; 132.2 Premaxil-lary tooth crowns incisiform and reduced in size;188.1 Sacral neural spines fused to form lamina; -240.0 Humeral ends little or not expanded; -316.0Caudal portion of pubic boot same length as cranialportion; 357.1 Cranial protuberance on fibula belowexpansion; 369.1 Metatarsus elongate relative toother theropods of same femoral length; 371.1Metatarsal cross-section deeper craniocaudallythan mediolaterally at midshaft; -386.0 Pedal ungualII subequal to pedal ungual III.
As discussed above, Arctometatarsalia is de-fined as Ornithomimus and all taxa sharing a morerecent common ancestor with Ornithomimus thanwith Neornithes (HOLTZ, 1996b). In half the mostparsimonious trees found in this study (Fig. 3A, 4),Arctometatarsalia includes only Tyrannosauridaeand Ornithomimosauria; in the other half, Troodonti-dae is included as well. As HOLTZ (1994) noted,many of the characters that unite tyrannosauridsand ornithomimosaurs (and troodontids) are foundin the locomotory apparatus, particularly in themetatarsus but also in the pelvis and caudal region.Some of these characters are also found in variouscombinations in other taxa (e.g., Elaphrosaurus,Coelurus, Caenagnathidae, mononykine alvarez-saurids), but no other taxa demonstrate the posses-sion of all of these features in the same animal (withthe exception of Troodontidae). Thus, the majority ofthe characters uniting ornithomimosaurs and tyran-nosaurids outside of other theropods are associatedwith higher cursorial ability (HOLTZ, 1995b) andmight have been convergently acquired by thesetwo different lineages near the base of Maniraptori-formes (as in SERENO, 1997; MAKOVICKY & SUES,1998).
However, there are other features that unite ty-rannosaurids and ornithomimosaurs in the presentstudy. Some have to do with the forelimb, but couldagain be explained by the reduced (or at least al-tered) grasping ability in both tyrannosaurids and or-nithomimosaurs relative to other coelurosaurs(HOLTZ, 1994). Unlike all other coelurosaurs (again,except for troodontids), the premaxillary teeth of ty-rannosaurids and the basal ornithomimosaur Pele-canimimus are incisiform (132.2), with both carinaeof each tooth being placed along the same planeperpendicular to the main axis of the skull (differingfrom typical avetheropods, in which the premaxillaryteeth are asymmetrical). Furthermore, the morphol-ogy of the nasals and of rostral portion of the frontals(25.1, 39.1) of basal tyrannosaurids and ornithomi-
mosaurs differs from that of other theropods (exceptfor troodontids). Also, as WITMER (1997) noted, or-nithomimosaurs and tyrannosaurids are the onlytwo lineages of non-avian theropods known to pos-sess squamosal recesses (55.1).
As noted by SERENO (1997), there are no possi-ble phylogenetic positions for Troodontidae that donot result in some level of homoplasy (convergenceor reversals) among maniraptoriform coelurosaurs.Indeed, as in HOLTZ (1994), troodontids were foundto be arctometatarsalians closer to ornithomimo-saurs than to tyrannosaurids in half of the most par-simonious trees in the present analyses. Thefollowing synapomorphies would support such aplacement (only those in all trees or under delayedtransformation are listed): 7.1, 8.1, 25.1, 39.1, 60.1,71.1, 72.1, 95.1, 132.2, 198.1, 206.1, -278.0, 287.1,-316.0, 357.1, 363.1, 369.1, 371.1, 373.1, 375.2,377.1, 379.2. Those characters not in this list butcurrently listed as occurring in all optimizations fornode cc are found in Tyrannosauridae and one orboth ornithomimosaur OTUs: these would be re-garded as synapomorphies of the expanded Arcto-metatarsalia (including Troodontidae) underaccelerated transformation. Additionally, tyranno-saurids and troodontids share a well-developedsagittal crest on the dorsal surface of the parietals(43.1), unlike ornithomimosaurs and indeed mostother coelurosaurs.
Following HOLTZ (1994, 1996b), Bullatosauria isdefined as all descendants of the most recent com-mon ancestor of Troodon and Ornithomimus. Bulla-tosauria was supported on many (primarily cranial)characters. WITMER (1997) and MAKOVICKY &NORELL (1998) observed several additional cranialfeatures shared by troodontids and ornithomimo-saurs. THULBORN (1984) and PÉREZ-MORENO et al.(1994) found additional character support for atroodontid-ornithomimosaur clade. However, asdiscussed below, troodontids are supported here asbasal paravian maniraptorans in half of the equallyparsimonious trees in this study. Under this topol-ogy, the clade defined by all descendants of the mostrecent common ancestor of Troodon and Or-nithomimus is exactly the same clade as that de-fined by the all descendants of the most recentcommon ancestor of Neornithes and Ornithomimus.Thus, Bullatosauria becomes a junior subjectivesynonym of Maniraptoriformes under this topology.Alternatively, when Troodontidae is placed as thesister group to Ornithomimosauria (and Bullatosau-ria is thus not the same clade as Maniraptoriformes),the following synapomorphies would support such anode (only those found under all optimizations andunder delayed transformation are shown): 1.1, 18.1,32.1, 46.1, 88.1, 93.1, 94.1, 98.1, 101.1, -116.0,
Thus, there is considerable support for a bullato-saurian arctometatarsalian position for Troodonti-dae. However, the manus of Troodont idaeresembles those of non-tyrannosaurid, non-ornithomimosaurian coelurosaurs in several fea-tures, although these might be explainable as the re-tention of the primitive state, since lost in otherarctometatarsalians. Similarly, the ischia of troodon-tids more closely resemble those of oviraptoro-saurs, dromaeosaurids, and avialians in being lessthan two thirds the length of the pubis (320.1) andhaving a distally placed obturator process (323.2).This might plausibly be the basal condition for Mani-raptoriformes, with the condition in Tyrannosauri-dae and Ornithomimidae representing novelextensions of the sub-process portion of the is-chium, but this ad hoc explanation would require ad-ditional evidence (for example, discovery of theischia of basal members of the tyrannosaurid and or-nithomimosaur lineages).
It should be noted, however, that the most com-plete skeleton of Troodontidae currently described,that of the type specimen of Sinornithoides youngiRUSSELL & DONG, 1993b indicate that some troo-dontid features once thought to be similar to dro-maeosaurids, avialians, and oviraptorosaurs arenow known to resemble the condition in ornithomi-mosaurs. For example, unlike most other manirap-toriform coelurosaurs, metacarpal III is subequal inlength to metacarpal II (rather than clearly shorter) introodontids and ornithomimosaurs (263.0), and (asin non-maniraptorans) metacarpal III is unbowed(265.0). While the latter is most parsimoniously ex-plained as the retention of a primitive trait, the formerwould best explained a single reversal in the com-mon ancestor of all bullatosaurs if a troodontid-ornithomimosaur clade were supported.
Siamotyrannus isanensis BUFFETAUT, SUTEE-THORN & TONG, 1996 is a recently discovered formfrom the Early Cretaceous (?Barremian) of Thai-land, purported to be an ancestral tyrannosaurid, asis the Late Jurassic North American species Stoke-sosaurus clevelandi MADSEN, 1976. These taxawere not included in the present analysis, pendingcompletion of preparation of additional specimensand hitherto unreported skeletal elements of thesespecies (E. BUFFETAUT, pers. commun. 1998;CHURE & MADSEN, 1998). The former taxon, as wellas the fragmentary Labocania anomala MOLNAR,1974 are the only theropods other than tyranno-saurids and ornithomimosaurs known to possess apronounced semicircular scar on the caudal surfaceof the ischium, just distal to the iliac process (326.1):these taxa thus might be arctometatarsalians. Itemi-rus medullaris KURZANOV, 1976, known only from a
braincase, may be related to Stokesosaurus and/ortyrannosaurids (CHURE & MADSEN, 1998) or to dro-maeosaurids (CURRIE & ZHAO, 1993b; CURRIE,1995). Premaxillary teeth with the diagnostic U-shaped horizontal cross-section currently onlyknown in Tyrannosauridae have been reported fromthe ?Aptian-Albian of Japan (M. MANABE, pers. com-m. 1997).
NODE dd. ORNITHOMIMOSAURIA
ALL: 1.1 Skull shape elongate and platyrostral,with obtuse triangular paracoronal cross section;6.1 Premaxilla long and pointed, with long nasal pro-cess; 8.2 Maxillary process of premaxilla extremelylong, extends caudally from the caudal margin of theexternal naris for a distance greater than the rostro-caudal length of the external naris; 18.1 Maxillaryfenestra long and low; 19.1 Promaxillary fenestradorsal to maxillary fenestra; 32.1 Lacrimal caudalprocess at dorsal surface, lacrimal T-shaped; 46.1Orbit margin with raised rim; 98.1 Parabasisphenoidbulbous capsule; 101.1 Occipital region directedventrocaudally; 136.1 Neck length twice or moreskull length; 141.1 Craniodorsal rim of axial neuralspine convex curve in lateral view; 163.1 Caudalcervical postzygapophyses elongate; 201.3 Shaft ofcervical ribs short (less than twice centrum length)and slender; 213.1 Acromion in scapula reduced;250.1 Ulnar and radial ends closely joined, even bysyndesmosis; -255.0 Semilunate carpal block ab-sent; -263.0 Metacarpal III length subequal to meta-carpal II; -264.0 Metacarpal III width not very muchnarrower (greater than 50%) than metacarpal II;269.1 Metacarpal-phalangeal joints not hyperexten-sible, extensor pits on metacarpals I-III reduced;276.1 Flexor tubercle of unguals poorly developedand distally placed; 280.1 Pollex shape stout and ro-bust, dorsoventrally compressed, with proximal ar-ticular surface quadrangular.
ACCTRAN: 3.3 Number of premaxillary teethseven; 85.1 Orbitosphenoid absent; 93.1 Cranialtympanic recess invades basisphenoid; 94.1 Inter-nal foramen of facial nerve cranioventral to vestiblo-cochlear nerve; 107.1 Symphyseal region ofdentary medially recurved; -114.0 Caudal surangu-lar fenestra small pit; 126.1 Number of teeth greaterthan 100; 128.2 Tooth serrations absent; 127.1 Den-tary teeth more numerous and smaller than maxil-lary teeth; 130.1 Tooth roots constricted; 135.2Interdental plates absent in dentary; -168.0 Apicesof dorsal neural spines unexpanded; 182.1 Capitu-lar facet of dorsal ribs situated dorsal to lamina, onprezygapophyseal base; -195.0 Proximal caudal zy-gapophyses short; 260.2 Metacarpal I subequal tometacarpal II in length; 289.1 Fossa for origin of M.cuppedicus on ilium broad; 348.1 Lateroproximal
29
A NEW PHYLOGENY OF THE CARNIVOROUS DINOSAURS
condyle (fibular condyle) on proximal end of tibiasmall and medially situated.
DELTRAN: -37.0 Prefrontals well exposed onskull roof; -54.0 Postorbital frontal process sharplyupturned; -116.0 Horizontal shelf on lateral surfaceof surangular, rostral and ventral to the mandibularcondyle absent or faint ridge; 158.1 Cranial cervicalcentra extend beyond caudal extend of neural arch;251.1 Distal carpal shape flat and discoidal, no dis-tinct articular surfaces.
Following PADIAN, HUTCHINSON & HOLTZ (1999),Ornithomimosauria is defined as all descendants ofthe most recent common ancestor of Pelecani-mimus and Ornithomimus.
The recently described Pelecanimus polyodon ofthe Early Cretaceous (Barremian) of Spain demon-strates many dental characteristics also found introodontids, but lost in the (mostly) edentulous Or-nithomimidae. The Early Cretaceous (?Aptian-Albian) Harpymimus okladnikovi, coded here withinOrnithomimidae, is more primitive than Pelecani-mimus in the retention of a metacarpal I muchshorter than metacarpal II in length. This Asiantaxon is being restudied by Osmólska and Pérez-Moreno, and may prove to l ie outs ide thePelecanimimus-Ornithomimidae (proper) clade infuture analyses. Also of interest is the recent reportof ornithomimosaurian material from the Aptian-Albian of Australia (RICH & VICKERS-RICH, 1994)and from the Barremian of Thailand (BUFFETAUT etal., 1995; SUTEETHORN et al., 1995).
NODE ee. MANIRAPTORA
ALL: 10.1 Premaxilla and nasal do not meet sub-narially; -57.0 Squamosal does not constrict lateraltemporal fenestra; 172.1 Caudal edge of dorsal zy-gapophyses overhangs centrum; 203.1 Medial gas-tral segment shorter than lateral segment; 298.1Postacetabular process of ilium with concave cau-dal margin; 320.1 Ischium less than 66% length ofpubis.
ACCTRAN: 89.1 Lateral depression surroundingopening to middle ear; 192.1 Caudal neural spineslimited to caudals I-IX; 253.2 Distal carpal I blockbroadly overlaps metacarpal II dorsally and ven-trally; 293.1 Preacetabular portion of ilium signifi-cantly longer than postacetabular portion; 381.1Pedal digit IV larger than II and closer to III in length.
DELTRAN: 37.1 Prefrontals reduced or absent; -54.0 Postorbital frontal process sharply upturned; -116.0 Horizontal shelf on lateral surface of surangu-lar rostral and ventral to the mandibular condyle ab-sent; 158.1 Cranial cervical centra extend beyondcaudal extent of neural arch; -357.0 Cranial protu-berance on fibula below expansion absent; -371.0
Metatarsals subequal or wider mediolaterally thancraniocaudally at midshaft; 386.1 Pedal ungual IIsignificantly longer than pedal ungual III.
In the present study, Maniraptora includes notonly birds but also dromaeosaurids, oviraptoro-saurs, therizinosauroids, and compsognathids (andtroodontids in half of the equally parsimonioustrees). This composition is similar to that found byGAUTHIER (1986) (although therizinosauroids, thencalled "segnosaurs", were at the time considerednon-theropods). The conclusions here differ fromHOLTZ (1994), where dromaeosaurids were the onlynon-avian theropod lineage considered closer tobirds than to Ornithomimus. Unlike SERENO (1997),tyrannosaurids were not found here to share a morerecent common ancestor with birds than with Or-nithomimus.
Compsognathidae is here considered to com-prise Compsognathus longipes WAGNER, 1861 andSinosauropteryx prima JI & JI, 1996. These taxashare derived features in an enlarged phalanx 1 ofmanual digit I (with shaft diameter greater than thatof the radius) and fan-shaped neural spines on thedorsal vertebrae (CHEN, DONG & ZHEN, 1998). Boththese taxa are also characterized by tails withgreater than 55 caudal vertebrae (more than thoseof all other coelurosaurs) (190.0) and by ischia with aslight expansion of the distal ischium (327.0). Theformer of these traits is most parsimoniously ex-plained by a reversal, while the latter might be a re-tention of the primitive condition (if the pointedischial tip is convergent in tyrannosaurids and ad-vanced maniraptorans) or a reversal (if the conditionin arctometatarsalians and maniraptorans repre-sent a single evolutionary event): see Discussionbelow. As with Scipionyx, this taxon is unspecializedcompared to most other advanced coelurosaurs,and so may be very informative with regard to thecondition of the ancestral maniraptoriform and theancestral maniraptoran.
MAKOVICKY & SUES (1998) considered the pres-ence of medial gastral segments shorter than the lat-eral segments as synapomorphic of a troodontid-dromaeosaurid clade, not present in ornithomimo-saurs, tyrannosaurids, and non-coelurosauriantheropods. However, compsognathids appear todemonstrate the same condition. As such, and giventhe current poor understanding of the gastralia intherizinosauroids, oviraptorosaurs, and basal birds,this feature (203.1) is most parsimoniously regardedhere as a maniraptoran synapomorphy under the to-pology placing troodontids as paravians; if troodon-tids are bullatosaurians, the origin of this derivedstate is ambiguous.
NODE ff.
30
T.R. HOLTZ, JR.
ALL: 130.1 Tooth roots constricted; 151.1 Epipo-physes on cervical vertebrae placed proximally;241.1 Deltapectoral crest on humerus expandedand offset from humeral shaft; 249.1 Ulnar facet forradius transversely expanded and concave; 296.1Caudodorsal margin of ilium curves caudoventrally;297.1 Postacetabular ala of ilium acuminate; 299.1Supracetabular crest on ilium absent; 323.2 Obtura-tor process of ischium distally placed; 327.1 Ischialfoot absent; 374.1 Metatarsal IV longer than meta-tarsal II and closer to metatarsal III in length.
ACCTRAN: 32.1 Lacrimal caudal process at dor-sal surface, lacrimal T-shaped; 126.1 Number ofteeth greater than 100; 127.1 Dentary teeth morenumerous and smaller than maxillary teeth; 128.1Teeth with large denticles; 163.1 Caudal cervicalpostzygapophyses elongate; 166.1 Ventral process(hypapophyses) on cervicodorsal vertebrae presentas small protrusions; 235.1 Humeral shaft sigmoid;236.1 Humeral head offset and emarginated ven-trally by groove; 243.1 Humeral entepicondyleprominent; 245.1 Ulnar shaft bowed caudally; 220.1Metacarpal III bowed laterally; 281.1 Manual un-guals II and III with small nubbin proximodistally;284.1 Manual unguals with extreme curvature;299.1 Supracetabular crest on ilium absent; 337.2Fourth trochanter of femur absent; 384.1 Pedal un-guals III and IV vertically oval in cross-section.
DELTRAN: 72.1 Secondary palate well ossifiedfrom premaxilla through one-half the length of theventral surface of the maxilla; 103.1 Occipital con-dyle with constricted neck; -223.0 Sternum shaperelatively round; 240.1 Humeral ends well ex-panded, greater than 150% midshaft diameter;253.2 Distal carpal I block broadly overlaps meta-carpal II dorsally and ventrally.
This unnamed clade (comparable to the re-defined "Maniraptora" of SERENO (1997, 1998)) isvery well supported based on character evidence(see also GAUTHIER, 1986). Although Troodontidaeis only weakly supported within this clade in the pres-ent analysis, and Therizinosauroidea was placedoutside it in the analysis of SERENO (1997, 1998),most recent workers have recovered a clade com-prised of oviraptorosaurs, dromaeosaurids, andbirds to the exclusion of ornithomimosaurs or tyran-nosaurids: GAUTHIER (1986); SERENO (1997, 1998);SUES (1997); MAKOVICKY & SUES (1998); NOVAS &POL (in press).
Although the derived character state "tooth rootsconstricted" (130.1) was found to be synapomorphicfor node ff, this condition is present only in some pre-maxillary teeth of one member of this clade, Dro-maeosauridae (CURRIE & ZHAO, 1993b: fig. 6).Lateral (maxillary and dentary) teeth of dromaeo-saurids do not show this condition. Additionally, the
tooth characters 126.1, 127.1, and 128.1, optimizedas present at node ff under accelerated transforma-tion, represent the similarities in the teeth of therizi-nosauroids and troodontids. Dromaeosaurids lackthese features, and retain the primitive state forthese characters.
In the summary cladogram, the opisthopubiccondition is considered to have evolved independ-ently in therizinosauroids and eumaniraptorans (seeDiscussion below). However, if troodontids aremoved to a bullatosaurian arctometatarsalian posi-tion (see above), opisthopuby (309.3) and an asso-ciated transformation of the ilium (306.1) becomeambiguously polarized. These character stateswould be either synapomorphic for node ff, and sec-ondarily lost in Microvenator plus Oviraptorosauria,or is independently evolved in the dromaeosaurid-bird clade and in therizinosauroids. MAKOVICKY &NORELL (1998) also noted the ambiguous nature ofthis character. It might be speculated that the convexcurvature of the oviraptorosaurian pubis (310.1)might represent a "re-propubic" state derived fromthe opisthopubic condition: however, additional datawould be needed to support this suggestion.
NODE gg.
ALL: 2.1 Premaxillary teeth absent, presumablycovered with rhamphotheca; 6.1 Premaxilla longand pointed, with long nasal process; -8.0 Maxillaryprocess moderately long, premaxilla participatesbroadly in ventral surface of external naris; -30.0Lacrimal not exposed on skull roof; 40.1 Frontal verybroadly exposed on skull roof, postorbital ramusdoes not project abruptly laterally from the orbitalmargin; 74.1 Vomer limited to rostral region; 79.1Palatine fenestra (between ectopterygoid and pala-tine) closed; 100.2 Basipterygoid processes veryshort, fused to pterygoids; 107.1 Symphyseal regionof dentary medially recurved; -114.0 Caudal suran-gular foramen a small pit; 148.2 Postaxial cervicalpleurocoels two pairs present; -197.0 Transitionpoint in tail absent; 200.2 Distal caudals markedlyshorter than proximal caudals; 201.2 Shaft of cervi-cal ribs short (less than twice centrum length) andbroad; -208.0 Middle chevron shape gentle curva-ture; -209.0 Distal chevrons lacking cranial and cau-dal projections; 244.1 Ulnar facet on humerusexpanded, merges with entepicondyle; 292.1 Prea-cetabular ala of ilium greatly expanded vertically;335.3 Anterior trochanter of femur cylindrical incross section; 367.1 Medial tuber on calcaneum en-larged
Craniodorsal rim of axial neural spine convex curvein lateral view; 183.1 Sacral pleurocoels present;187.1 Caudalmost sacral centrum markedly smallerthan cranialmost sacral centrum; 222.1 Sternumcarina present; -272.0 Length of phalanx 3 of man-ual digit III/(sum of lengths of phalanges 1 + 2 of digitIII) greater than 100%; 275.1 Manual ungual, dorsaledge of articular facet with pronounced lip on dorsaledge; 289.1 Fossa for origin of M. cuppedicus on il-ium broad
Craniodorsal rim of axial neural spine convex curvein lateral view; 183.1 Sacral pleurocoels present;187.1 Caudalmost sacral centrum markedly smallerthan cranialmost sacral centrum; 222.1 Sternumcarina present; -272.0 Length of phalanx 3 of man-ual digit III/(sum of lengths of phalanges 1 + 2 of digitIII) greater than 100%; 275.1 Manual ungual, dorsaledge of articular facet with pronounced lip on dorsaledge; 289.1 Fossa for origin of M. cuppedicus on il-ium broad
DELTRAN: 7.1 Medial alae from premaxillaemeet in front of vomera; 121.1 Coronoid extremelyreduced or absent; -168.0 Apices of dorsal neuralspines unexpanded; -192.0 Caudal neural spinespresent beyond caudal X; 226.1 Forelimb (hu-merus+radius+manus)/hindlimb (femur+tibia+pes)length ratio greater than 50% but less than 120%;243.1 Humeral entepicondyle prominent; 281.1Manual unguals II and III with small nubbin proxi-modistally; 293.1 Preacetabular portion of ilium sig-nificantly longer than postacetabular portion; 299.1Supracetabular crest on ilium absent; -316.0 Caudalportion of pubic boot same length as cranial portion;337.2 Fourth trochanter on femur absent; 384.1Pedal unguals III and IV cross section vertically oval
As in RUSSELL & DONG (1993a), SUES (1997),and MAKOVICKY & SUES (1998) but unlike SERENO(1997), Therizinosauroidea was found to be mostclosely related to the oviraptorosaurs among Thero-poda. These taxa share numerous cranial and post-cranial synapomorphies. Of note is the fact thatmany of these derived features are reversals: insome cases, such as the apparent loss of a transi-tion point in the tail (-159.0) and related caudal trans-formations (-192.0, 200.2, -208.0, -209.0) and theexclusion of the lacrimal from the skull roof (-29.0),are reversals to a pre-neotheropod state. Also asno ted by MA K O V I C K Y & SU E S (1998) , thetherizinosauroid-oviraptorosaur clade shares withCeratosauria possession of two pleurocoels on thepostaxial cervicals (148.2).
NODE hh.
ALL: 104.1 Dentary teeth absent; -118.0 Externalmandibular fenestra large, horizontally oval; 156.1Caudal cervical neural arch forms X-shape in dorsalview; -169.0 Scars for interspinous ligaments termi-nate at apex of neural spine in dorsal vertebrae;171.1 Dorsal transverse processes short, wide andonly slightly inclined; 176.1 Dorsal centrum trans-verse section wider than high; 310.1 Pubic shaft withmarked concave curvature cranially; 358.1 Fibulartubercle for M. iliofibularis (="anterolateral process")laterally projecting.
ACCTRAN: 5.1 Premaxilla subnarially verydeep, main body taller dorsoventrally than long ros-
trocaudally; -10.0 Premaxilla and nasal meet sub-narially; 12.1 Maxillary teeth absent; 29.1 Nasal re-cesses present; 42.1 Frontals separated atmedialmost point of suture by rostral process of pa-rietals; 87.1 Paroccipital processes curving ven-trally and pendant; 109.1 Dentary rami widelydivergent caudally; -110.0 Overlap of dentary ontopostdentary bones; -111.0 Intramandibular joint ab-sent; 112.2 Dentary caudal depth greater than 220%depth of dentary symphysis; -115.0 Rostral ramus ofsurangular shallow; 122.1 Articular facet for man-dibular joint craniocaudally elongate and shallow;124.1 Retroarticular process elongated and taper-ing; 178.1 Dorsal column subequal to femur length;185.4 Number of sacrals six; -195.0 Proximal caudalzygapophyses short; -196.0 Caudal transverse pro-cesses present beyond caudal XV; 262.1 Metacar-pal II length about 50% or greater humerus length;265.1 Metacarpal III bowed laterally; -386.0 Pedalungual II subequal to pedal ungual III.
DELTRAN: 141.1 Craniodorsal rim of axial neu-ral spine convex curve in lateral view; 157.1 Cranialcervicals broader than deep on cranial surface, withkidney-shaped articular surfaces that are taller later-ally than at midline; 187.1 Caudalmost sacral cen-trum markedly smaller than cranialmost sacralcentrum; 232.2 Radius greater than 76% length ofhumerus; 235.1 Humeral shaft sigmoid; 245.1 Ulnarshaft bowed caudally; 275.1 Manual ungual, dorsaledge of articular facet with pronounced lip on dorsaledge; 289.1 Fossa for M. cuppedicus on ilium broad.
NODE ii. OVIRAPTOROSAURIA
ALL: 106.1 Dentary symphysis fused; 191.2Caudal pleurocoels present in centrum.
ACCTRAN: None.
DELTRAN: 12.1 Maxillary teeth absent; 87.2 Pa-roccipital process curving ventrally and pendant; -88.0 Basicranium pneumatization minimal to mod-erate, but no expansion of basisphenoid; -108.0Rostral half of mandible ventrally convex or straight;-110.0 Overlap of dentary onto postdentary bones; -111.0 Intramandibular joint absent; -115.0 Rostralramus of surangular shallow; 122.1 Articular facetfor mandibular joint craniocaudally elongate andshallow; 124.1 Retroarticular process elongatedand tapering; 183.1 Sacral pleurocoels present;185.4 Number of sacrals six; 186.2 Sacrals III-V dor-soventrally flattened; 188.1 Sacral neural spinesfuse to form lamina; -195.0 Proximal caudal zygapo-physes short; 265.1 Metacarpal III bowed laterally.
Following the phylogenetic definitions in PADIAN,HUTCHINSON & HOLTZ (1999), Oviraptorosauria isdefined as all descendants of the most recent com-mon ancestor of Oviraptor and Chirostenotes. Assuch, Microvenator is excluded from Oviraptorosau-
32
T.R. HOLTZ, JR.
ria proper in one out of the two topologies of mani-raptoriform relationships in this study (Fig. 3C).Nevertheless, this small Early Cretaceous (?Aptian-Albian) taxon is clearly more closely related to Ovi-raptoridae and Caenagnathidae than to any otherknown taxon. As in SUES (1997) and MAKOVICKY &SUES (1998), this study found very strong supportfor uniting Oviraptoridae and Caenagnathidae to theexclusion of Therizinosauroidea. Note that thisstudy agrees with CURRIE, GODFREY & NESSOV(1993), SUES (1997), MAKOVICKY & SUES (1998),and SERENO (1997), and disagrees with HOLTZ(1994) in recognizing the oviraptorosaurian natureof Caenagnathidae ("Elmisauridae" in the latterstudy), necessitating an independent evolution ofthe arctometatarsus in caenagnathid oviraptoro-saurs and in true arctometatarsalians (and in troo-dontids, if they are not arctometatarsalians, and inmononykine alvarezsaurids: see also Discussionbelow).
NODE jj. PARAVES
ALL: 162.1 Carotid process on caudal cervicalvertebrae; 194.1 Centra of caudals I-V box-like withincreased flexural capability; 197.3 Transition pointin caudals I-IX; 204.1 Chevron transition betweencaudal X and XVII; -274.0 First phalanx of pollex lessthan or subequal to length of metacarpal II; 383.1Pedal digit II hyperextensible; 385.1 Pedal ungual IIsickle-shaped (blade-like cross section and highlyrecurved).
ACCTRAN: 92.1 Posttympanic recess confinedto columnar process; 101.1 Occipital region directedventrocaudally; 102.1 Foramen magnum taller thanwide; 119.1 Splenial with extensive triangular expo-sure in lateral view between dentary and angular;129.1 Posterior serrations much larger than anteriorserrations in maxillary and dentary teeth; 135.2 In-terdental plates absent in dentary; 198.1 Midcaudalvertebrae with moderately long prezygapophyses,extending more than one half but less than one cen-trum length; 200.1 Distal caudals more than 130%length of proximal caudals; 210.1 Distal chevroncranial and caudal bifurcations; 379.2 Metatarsal Iplaced distally.
DELTRAN: 32.1 Lacrimal caudal process at dor-sal surface present, lacrimal T-shaped; -67.0 Quad-rate foramen large and situated between quadrateand quadratojugal; 81.2 Ventral ectopterygoid re-cess present and subcircular; 91.1 Branches of in-ternal carotid artery enter hypoglosseal fossathrough single common opening; 140.1 Axial neuralspine compressed mediolaterally; 157.1 Cranialcervicals broader than deep on cranial surface, withreniform (kidney-shaped) articular surfaces that aretaller laterally than at midline; 166.1 Ventral pro-cesses (hypapophyses) on cervicodorsal vertebrae
present as small protrusions; 192.1 Caudal neuralspines limited to caudals I-IX; 235.1 Humeral shaftsigmoid; 236.1 Humeral head offset and emargi-nated ventrally by groove; 245.1 Ulnar shaft bowedlaterally; 284.1 Manual unguals extremely curved;381.1 Pedal digit IV larger than II and closer to III inlength.
SERENO (1997) coined the term "Paraves" forbirds and all theropods sharing a more recent com-mon ancestor with birds than with oviraptorosaurs;in the present analysis this clade contains Dromaeo-sauridae (and Troodontidae in half the trees) as wellas birds. A clade containing troodontids, dromaeo-saurids, and birds has been recovered by a numberof studies (GAUTHIER, 1986; SERENO, 1997, 1998;FORSTER et al., 1998; MAKOVICKY & SUES, 1998;NOVAS & POL, in press). HOLTZ (1994) has been oneof the few explicit analyses to discover a different re-lationship, with troodontids closer to ornithomimo-saurs than to birds.
However, unlike previous studies supportingtroodontid-dromaeosaurid-bird monophyly, thisa n a l y s i s d i d n o t s u p p o r t a t r o o d o n t i d -dromaeosaurid clade to the exclusion of birds (as inGAUTHIER, 1986 (where it was coded as such a pri-ori); SERENO, 1997, 1998; MAKOVICKY & SUES,1998; NOVAS & POL, in press) nor a troodontid-birdclade to the exclusion of dromaeosaurids (as in FOR-STER et al., 1998). Instead, troodontids were foundto lie outside the dromaeosaurid-bird clade Eumani-raptora in all twenty most parsimonious trees (andindeed to lie outside Maniraptora in half the trees).
Nevertheless, several characters do support atroodontid-dromaeosaurid clade (119.1, 129.1,210.1) while others support a troodontid-bird group-ing (92.1, 101.1, 102.1, 135.2, 198.1, 379.2). Itshould be noted here, however, that Troodontidaewas incorrectly coded as possessing ischiadic ter-minal processes separate (328.1 of this analysis) inthe study of FORSTER et al. (1998), resulting in a ba-sal avialian position for this clade. The terminal pro-cesses of the ischia of troodontids observed by thepresent author are indeed in contact, as attested bythe flat articular surfaces in some specimens (e.g.,Troodon formosus, RTMP 86.77.2) and fusion of theischiadic symphyses in others (e.g., Saurornithoi-des mongoliensis, AMNH 6516) (see also NORELL &MAKOVICKY, 1997). Significantly, as discussedabove, additional character evidence equallystrongly supports a sister group relationship be-tween ornithomimosaurs and troodontids outside ofManiraptora. Troodontids thus remain one of themost poorly resolved of maniraptoriform clades withregards to their phylogenetic position, despite thefact that this taxon is known from a number of excel-lent specimens.
33
A NEW PHYLOGENY OF THE CARNIVOROUS DINOSAURS
Curiously, the presence of Troodontidae, Dro-maeosauridae, and Rahonavis as serial sister taxato Aves strongly supports the presence of a hyperex-tensible digit II (383.1) with a sickle-shaped claw(385.1) as the ancestral condition for birds. In treeswhere Troodontidae is considered an arctometatar-salian, however, the sickle claw is equally parsimo-niously considered as basal to Eumaniraptora(under accelerated transformation) or as conver-gently acquired by dromaeosaurids and Rahonavis(under delayed transformation). A recently de-scribed fragmentary taxon, Megaraptor namun-huaiquii NOVAS, 1998, also possesses a sickle-shaped pedal digit II ungual. However, NOVAS(1998) noted that this form lacked derived features(such as the bowed ulna) that characterize dro-maeosaurids and troodontids.
Related to this, as observed by PAUL (1988),SERENO (1997), and FORSTER et al. (1998) is theshared presence of a hyperextensible pedal digit II(383.1) in troodontids, dromaeosaurids, Rahonavis,Archaeopteryx, and some basal ornithothoracines.In the present study, this character state is consid-ered synapomorphic for Paraves, and lost in Al-varezsauridae and advanced ornithothoracinebirds. The presence of this structure in some forms(such as Archaeopteryx) which lack a trenchantsickle-claw suggests that the hyperextension ofpedal digit II was employed for purposes other thanpredation (OSTROM, 1969a, b) in at least someparavians. Whether this structure may have origi-nally served a predatory function, and was exaptedinto a scansorial function (or vice versa) lie beyondthe scope of the present study.
Of minor note: NORELL & MAKOVICKY (1997) cor-rectly identified a typographical error in the descrip-tion of a character state uniting dromaeosaurids andbirds used in HOLTZ (1994). They correctly observedthat this character state (381.1 in the present study)is in fact pedal digit IV is longer than pedal digit II.(The character state incorrectly written in HOLTZ(1994) as "pedal digit II longer than pedal digit IV" ac-tually describes the condition in Dilophosaurus(WELLES, 1984)).
NODE kk. EUMANIRAPTORA
ALL: 63.1 Quadratojugal T-shaped; 87.1 Paroc-cipital process with conspicuous twist in the distalend orienting distal surface more dorsally than proxi-mal region; 125.1 Vertical columnar process on ret-roarticular process; 144.1 Axial epipophysesprominent; 207.1 Proximal chevron shape dorsov-entrally depressed; 237.1 Internal tuberosity (= ven-tral tubercle) on proximal end of humerus welldifferentiated and angular; 238.1 Internal tuberosityon proximal end of humerus craniocaudally com-pressed and longitudinally elongate; 262.1 Metacar-
pal II about 50% or greater humerus length; 265.1Metacarpal III bowed laterally; 306.1 Pubic pedun-cle of ilium extends more ventrally than ischiadic pe-duncle; 309.3 Opisthopubic; 334.2 Anterior (=lesser) trochanter nearly confluent with femoralhead and greater trochanter; 343.1 Adductor fossaand associated caudodistal crest of distal femur re-duced or absent; 348.1 Lateroproximal condyle(fibular condyle) on proximal end of tibia small andmedially situated; 350.2 Crista fibularis well devel-oped; 351.2 Crista fibularis distally placed.
ACCTRAN: 217.2 Coracoid subrectangular, dor-soventral depth more than 130% of craniocaudalwidth.
DELTRAN: -89.0 Lateral depression surround-ing opening to middle ear absent; -126.0 Number ofteeth less than 100; -127.0 Dentary and maxillaryteeth subequal in number and size; 226.1 Forelimb(humerus+radius+manus) /h indl imb (femur+tibia+pes) length ratio greater than 50% but lessthan 120%; 232.2 Radius length greater than 76%humerus length; 243.1 Humeral entepicondyleprominent; 316.2 Pubic boot cranial portion absent; -384.0 Pedal unguals III and IV cross-section subtri-angular.
PADIAN, HUTCHINSON & HOLTZ (1999) proposed"Eumaniraptora" for the clade comprised of all de-scendants of the most recent common ancestor ofDeinonychus and Neornithes. Note that this term isnot synonymous with SERENO's (1997) Paraves,which represents a more inclusive, stem-definedclade containing the node-defined Eumaniraptora.In the present study Troodontidae represents aparavian taxon that was not also a eumaniraptoran(in half the trees; in the other half, it is an arctometa-tarsalian clade).
In the phylogenetic taxonomy of PADIAN,HUTCHINSON & HOLTZ (1999), the two namedbranches of Eumaniraptora are DeinonychosauriaCOLBERT & RUSSELL, 1969 (Deinonychus and alltaxa sharing a more recent common ancestor withDeinonychus than with Neornithes) and AvialaeGAUTHIER, 1986 (Neornithes and all taxa sharing amore recent common ancestor with Neornithes thanwith Deinonychus). In the present study, as in HOLTZ(1994), but unlike SUES (1997), SERENO (1997), andMAKOVICKY & SUES (1998), Troodontidae was notfound to be a member of Deinonychosauria: seeabove. The only OTU within Deinonychosauria inthe present analysis is Dromaeosauridae.
Dromaeosaurids thus remain the closest knownlineage of "traditional" theropod to birds. Placingtroodontids as close or closer to birds than dromaeo-saurids would require the shared derived charactersdescribed above to have been either a) conver-gently acquired in Dromaeosauridae and Avialae or
34
T.R. HOLTZ, JR.
b) present in basal Paraves and subsequently lost inTroodontidae. (See Discussion below)
Of additional note, several character state rever-sals listed in the DELTRAN category for this clade (-89.0, -126.0, -127.0) are required in this topology asthe derived state is present in both troodontids onone branch and therizinosauroids and/or oviraptoro-saurs on the other. Thus, under some optimizationsthese characters were hypothesized to be presentancestrally in Paraves, and would then have to bereversed in Eumaniraptora. However, these condi-tions might alternatively support a sister group rela-t i o n s h i p b e t w e e n t r o o d o n t i d s a n d t h etherizinosauroid-oviraptorosaur clade to the exclu-sion of Paraves (see Discussion).
NODE ll. AVIALAE
ALL: 173.1 Vertebral foramen/cranial articularfacet ratio (vertical diameters) of dorsals 0.4 orgreater; 190.2 Number of caudals less than 25;216.1 Glenoid oriented laterally; 246.1 Proximal ul-nar shaft arched; 293.1 Preacetabular portion of il-ium significantly longer than postacetabular portion;325.1 Ischial proximodorsal process just distal to il-iac process; 328.1 Ischiadic terminal processesseparate; -355.0 Proximal region of fibular medialface flat; -374.0 Metatarsal IV subequal in length tometatarsal II; 380.2 Metatarsal I completely reverted
ACCTRAN: 1.2 Skull shortened and platyrostral,with acute triangular paracoronal cross-section; -4.0 Premaxillary symphyseal region V-shaped inventral view; 6.1 Premaxilla long and pointed withlong nasal process; 51.1 Postorbital-jugal contactabsent; 55.1 Squamosal recess; -64.1 Dorsal ramusof quadratojugal does not contact squamosal; 74.1Vomer extends caudally to basicranium; 76.2 Pala-tine triradiate (no jugal process); 82.2 Endocranialcavity greatly enlarged, temporal musculature failsto extend origin onto frontals; -103.0 Occipital con-dyle constricted neck absent; -114.0 Caudal suran-gular foramen small pit; 124.1 Retroarticularprocess elongated and tapering; 141.1 Craniodor-sal rim of axial neural spine convex curve in lateralview; -152.0 Caudal cervical epipophyses short; -169.0 Scars for interspinous ligaments terminate atapex of neural spine in dorsal vertebrae; 184.1 Firstsacral procoelous; 218.1 Coracoid caudoventralprocess length more than twice glenoid diameter;220.1 Coracoid angle with scapula at level of glenoidcavity sharp; 221.1 Sternal plates fused; 227.2 Fore-limb/presacral vertebral series length ratio about200% or more; 230.1 Humerus/ulna length ratio lessthan or equal to 100%; 247.1 Diameter of ulnar shaftmuch thicker than that of radius; -263.0 MetacarpalI I I length subequal to metacarpal I I ; 269.1Metacarpal-phalangeal joints not hyperextensible,extensor pits on metacarpals I-III reduced; 273.1
Pollex ends at level of mid-length of phalanx 1 of digitII; -277.0 Manual ungual, region palmar to ungualgroove wider than region dorsal to ungual groove;335.4 Anterior trochanter of femur forms tro-chanteric crest (fusion of greater and anterior tro-chanters); 360.2 Fibular distal end pinches out lessthan half way down tibia length
DELTRAN: 163.1 Caudal cervical postzygapo-physes elongate; -168.0 Apices of dorsal neuralspines unexpanded; -198.0 Midcaudal vertebraewith short prezygapophyses, extending less thanone half centrum length; -210.0 Distal chevron cra-nial and caudal bifurcations absent; 293.1 Preace-tabular portion of ilium significantly longer thanpostacetabular portion; -369.0 Metatarsus propor-tions moderate; 379.2 Metatarsal I placed at distalend of metatarsal II
NODE mm. AVES
ALL: 178.1 Dorsal column subequal to femurlength; -195.0 Proximal caudal zygapophyses short;313.2 Pubic apron strongly reduced transverselyand restricted to distal 25% or less of pubic length;323.3 Obturator process absent, caudoventral mar-gin of ischium smooth from obturator notch to tip; -385.0 Pedal ungual II same shape as other pedal un-guals
ACCTRAN: 171.1 Dorsal transverse processesshort, wide and only slightly inclined; 174.1 Dorsalhyposphene-hypantrum accessory articulations ab-sent; 177.1 Dorsal centrum ends biconvex
DELTRAN: 1.2 Skull shortened and platyrostral,with acute triangular paracoronal cross-section; -4.0 Premaxillary symphyseal V-shaped in ventralview; 6.1 Premaxilla long and pointed with long na-sal process; 51.1 Postorbital-jugal contact absent;55.1 Squamosal recess; -64.1 Dorsal ramus ofquadratojugal does not contact squamosal; 74.1 Vo-mer extends caudally to basicranium; 76.2 Palatinetriradiate (no jugal process); 92.1 Posttympanic re-cess confined to columnar process; 101.1 Occipitalregion directed ventrocaudally; 102.1 Foramenmagnum taller than wide; -103.0 Occipital condyleconstricted neck absent; -114.0 Caudal surangularforamen small pit; 121.1 Coronoid extremely re-duced or absent; -119.0 Splenial obscured or onlyslightly visible in lateral view; -120.0 Splenial withoutnotch on rostral margin for internal mandibular fen-estra; 128.2 Serrations absent; -132.0 Premaxillarytooth crowns conical; 141.1 Craniodorsal rim of axialneural spine convex curve in lateral view; -169.0Scars for interspinous ligaments terminate at apexof neural spine in dorsal vertebrae; 218.1 Coracoidcaudoventral process length more than twice gle-noid diameter; 220.1 Coracoid angle with scapula atlevel of glenoid cavity sharp; 221.1 Sternal plates
35
A NEW PHYLOGENY OF THE CARNIVOROUS DINOSAURS
fused; -263.0 Metacarpal III length subequal tometacarpal II; 273.1 Pollex ends at level of mid-length of phalanx 1 of digit II; 299.1 Supracetabularcrest on ilium absent; -386.0 Pedal ungual II sube-qual in length to pedal ungual III
GAUTHIER (1986) explicitly gave his new taxonAvialae a stem-based definition (p. 36), althoughsome authors (NOVAS & PUERTA, 1997; JI et al.,1998) have subsequently used this term as a node-defined taxon (all descendants of the most recentcommon ancestor of Archaeopteryx and modernbirds). In this study, one taxon was found to share amore recent common ancestor with neornithinebirds than with Deinonychus, but which were foundto lie outside the clade of Archaeopteryx plus Neor-nithes. This is the recently discovered species Ra-honavis ostromi (FORSTER et al., 1998) of the?Campanian of Madagascar. Similarly, the frag-mentary form Unenlagia comahuensis NOVAS &PUERTA, 1997 (of the Turonian of Argentina) wasalso found to lie within Avialae but outside of Aves insome of the most parsimonious trees in which it wasincluded. If future studies support this topology, orthose which place Unenlagia closer to modern birdsthan to Rahonavis, this would support an hypothesisof secondary (rather than primary) flightlessness inthe large-bodied Unenlagia. However, there is nophylogenetic evidence found here for hypotheses ofsecondary flightlessness in non-avialian manirapto-rans (dromaeosaurids, troodontids, oviraptoro-saurs, etc.) or other non-avialian coelurosaurs (assuggested by THULBORN (1984) and PAUL (1988)).
As mentioned previously, the pes of Rahonavisresembles that of troodontids and dromaeosauridsin the possession of a hyperextensible pedal digit IIterminating in a sickle claw. The pes of Unenlagia is,regrettably, unknown. Sickle clawed Megaraptor oc-curs in the same deposits as Unenlagia, but what lit-tle is known of the anatomy of Megaraptor suggeststhat it is more distantly related to birds than are dro-maeosaurids (NOVAS, 1998), while Unenlagia ap-pears to be a basal bird in this analysis and those ofNOVAS & PUERTA (1997) and FORSTER et al. (1998).
Because Rahonavis is incompletely known (e.g.,neither cranial nor manual material has been recov-ered), there are many characteristics shared by Ar-chaeopteryx and more advanced birds that may at alater date be found to be synapomorphic for a moreinclusive clade.
Unenlagia and Rahonavis share one potentialsynapomorphy (vertically oriented pubis, 263.3), al-though this character state is known in at least onespecimen of Archaeopteryx (WELLNHOFER, 1993;FORSTER et al., 1998).
The recently described Early Cretaceous taxaProtarchaeopteryx robusta JI & JI ,1997 and Caudip-
teryx zoui JI et al., 1998 were not included in thepresent analysis (but these spectacularly preservedtaxa are included in work in preparation by the pres-ent author). The preliminary phylogenetic analysisof JI et al. (1998) placed Caudipteryx as a non-avianavialian (following the taxonomy here), and Protar-chaeopteryx as either a non-avian avialian, a deino-nychosaur, or as the sister group to Eumaniraptora.
NODE hh. METORNITHES
ALL: -34.0 Slot in ventral process of lacrimal forjugal absent; 59.1 Jugal postorbital process absent;65.1 Quadrate articulates with both prootic andsquamosal, and the later contacts neither the quad-ratojugal nor the postorbital; 222.1 Sternum carinapresent; 223.1 Sternum longer craniocaudally thanwide mediolaterally; 224.1 Sternum much greaterthan coracoid length; 239.2 Internal tuberosity(=ventral tubercle) of humerus projected caudally,separated from humeral head by deep capital inci-sion; 242.1 Humeral distal condyle with only cranialaspect; 248.1 Ulnar distal condyle subtriangularshaped in distal view, with a dorsomedial condyle,and twisted more than 54 degrees with respect to theproximal end; 252.1 Carpometacarpus (distal car-pals fused to each other and to metacarpus); 258.1Metacarpal III present, without ungual; -350.1 Cristafibularis present, not well developed; 358.1 Fibulartubercle for M. iliofibularis (="anterolateral process")laterally projecting
ACCTRAN: 134.1 Dentary tooth implantation setin paradental groove; 166.2 Ventral processes (hy-papophyses) on cervicodorsal vertebrae very welldeveloped; 189.1 Synsacrum present in adults;259.1 Metacarpal II absent; -284.0 Manual ungualcurvature straight; -288.0 Iliac preacetabular fossafor M. cuppedicus absent; -320.0 Ischium greaterthan 75% length of pubis; 366.1 Astragalocal-caneum (astragalus fused to calcaneum); 368.1Tibiotarsus (astragalocalcaneum fused to tibia); -383.0 Pedal digit II not hyperextensible
DELTRAN: 177.1 Dorsal centrum ends bicon-vex; 184.1 First sacral procoelous
Following SERENO (1997, 1998), PADIAN &CHIAPPE (1998), and PADIAN, HUTCHINSON & HOLTZ(1999), and contra GAUTHIER (1986), the term Avesis used for the clade comprised of all descendants ofthe most recent common ancestor of Archaeopteryxand Neornithes (see the first four papers for justifica-tion). Unlike PAUL (1988), this analysis did not sup-port the hypothesis that dromaeosaurids were moreclosely related to Archaeopteryx than either are tomodern birds, nor the hypothesis that ornithomimo-saurs, oviraptorosaurs, and troodontids shared amore recent common ancestor with Neornithes thandid Archaeopteryx.
36
T.R. HOLTZ, JR.
As in the analyses of PERLE et al. (1993, 1994),CHIAPPE, NORELL & CLARK (1996, 1998), NOVAS(1996, 1997a), and FORSTER et al. (1998), the highlyapomorphic Alvarezsauridae were found to be birdsmore closely related to Neornithes than is Archae-opteryx (a result surprising to the present author). Asdiscussed in those previous works, and shown in thecharacter state lists above, alvarezsaurids werefound to share more derived characters with Orni-thothoraces (all descendants of the most recentcommon ancestor of Iberomesornis and Neorni-thes: see PADIAN, HUTCHINSON & HOLTZ, 1999). Itdid not support the conclusion of MARTIN (1997),whose phylogenetic analysis (itself methodologi-cally problematic, as the all-zero outgroup was usedas an OTU in that study) recovered an ornithomimo-saurian position for the alvarezsaurid Mononykusolecranus PERLE et al., 1993. Following PERLE et al.(1993), the term Metornithes is used for the cladecomprised of all descendants of the most recentcommon ancestor of Mononykus and Neornithes.
As NOVAS (1996, 1997a), NOVAS & POL (inpress), and SERENO (1997) observed, primitive al-varezsaurids (Alvarezsaurus calvoi BONAPARTE,1991 and Patagonykus puertai NOVAS, 1996) lacksome derived features found in both Ornithothora-ces and the derived mononykine alvarezsauridsMononykus, Parvicursor remotus KARHU & RAU-TIAN, 1996, and Shuvuuia deserti CHIAPPE, NORELL& CLARK, 1998: these character states, previouslyproposed as synapomorphies of Mononykus andOrnithothoraces (e.g., PERLE et al., 1993), are bestexplained as convergences between advanced al-varezsaurids and ornithothoracines. The presentanalysis agrees with NOVAS (1996, 1997a) and dis-agrees with SERENO (1997) and NOVAS & POL (inpress), however, in proposing that the lack of somederived features of the postcranium found in Ar-chaeopteryx and Ornithothoraces are reversals to apre-avian condition, rather than evidence of a non-avian phylogenetic position of Alvarezsauridae.
The presence of an arctometatarsus even morespecialized than that found in Caenagnathidae orArctometatarsalia in Mononykus and Parvicursor(377.2; see HOLTZ (1995b): p. 511) is interpreted asconvergence with the former two taxa, an hypothe-sis strongly supported by the lack of this condition inthe more basal alvarezsaurids Patagonykus and Al-varezsaurus or in other eumaniraptorans.
DISCUSSION
Although many attributes of theropod phyloge-netic history can be examined given the new hy-pothesis proposed here, three main aspects will bediscussed. These are: new distributions for derivedcharacter states previously hypothesized as syna-pomorphies of various theropod subclades; alterna-
tive combinations of various theropod taxa, in light ofthe character evidence presented here; and the im-plications for the present new phylogeny of theropoddinosaurs when mapped onto stratigraphic time.
REVISED DISTRIBUTION OF PREVIOUSSYNAPOMORPHIES OF THEROPOD SUBCLADES
The inclusion of many new characters and taxa inthe present analysis results, not surprisingly, in newdistributions for character states previously hy-pothesized to characterize various subclades oftheropods. Some of these characters are discussedbelow.
Prior to the extensive revision of archosaur facialpneumaticity by WITMER (1997), it was hypothe-sized that the small opening in the rostral region ofthe antorbital fossa of non-coelophysid ceratosaurswas homologous to the maxillary fenestra of teta-nurines (GAUTHIER, 1986; HOLTZ, 1994). However,as WITMER has cogently argued, this structure mightbe more appropriately homologized with the pro-maxillary fenestra, a structure previously thought tohave arisen only among more advanced tetanurines(HOLTZ, 1994; SERENO et al., 1994, 1996). The pro-maxillary fenestra (16.1) is present in Spinosauri-dae, Eustreptospondylus, Piatnitzkysaurus,Afrovenator, and most avetheropods, but is notfound in Torvosaurus. As such, the most parsimoni-ous set of trees for basal tetanurines suggest thatthis condition was present in the ancestor of all teta-nurines studied here, and that its lack in Torvosaurus(and in the derived caenagnathid and therizino-sauroid coelurosaurs) are secondary reversals.
Given that the promaxillary fenestra is not pres-ent in Ceratosaurus and in Coelophysidae (althoughboth these forms exhibit a small dimple which doesnot perforate the maxilla in approximately the samelocation, condition 16.3), but is present in Abelisauri-dae and Dilophosaurus, this character has an uncer-tain distribution among Ceratosauria as a whole. Asthe most parsimonious trees in the current study re-solve this character as present in basal tetanurines,it is considered to be present in Neotheropodaancestrally under accelerated transformation, andthus the absence of this structure in Ceratosaurusand Coelophysidae is explained by convergence.However, under delayed transformation it is opti-mized as absent in Ceratosauria ancestral, and thusevolving independently in tetanurines, abelisaurids,and Dilophosaurus.
The origin of the maxillary fenestra (17.1) is like-wise ambiguous, although it is not present in anyknown ceratosaurian. This structure can clearly beidentified if the promaxillary fenestra itself can alsobe demonstrated in the same specimen, as theopening between the promaxillary fenestra and the
37
A NEW PHYLOGENY OF THE CARNIVOROUS DINOSAURS
internal antorbital fenestra. This is clearly the case inAfrovenator and most carnosaurs and coeluro-saurs. In "Megalosaurus" hesperis (BMNH R332)the lateral aspect of the maxilla is not exposed, so itis uncertain whether the large opening visible fromthe medial side is a maxillary fenestra or a promaxil-lary fenestra (WITMER, 1997). The very large open-ings in the rostral part of the antorbital fossa ofMonolophosaurus and Giganotosaurus are difficultto homologize with other tetanurines: they might bevery large promaxillary fenestrae, true maxillary fen-estrae (in which case the promaxillary fenestraehave been lost), or structures representing the fu-sion of these two openings (a possibility suggestedby WITMER, 1997). In Carcharodontosaurus only asingle, smaller fenestra is present in the rostral por-tion of the antorbital fossa: again, it is uncertain if thisis the promaxillary fenestra or the maxillary fenestra.In this genus (as in the abelisaurids), the maxillaryantorbital fossa as a whole is reduced (15.2), result-ing in a very large internal antorbital fenestra.
In any case, the lack of both promaxillary andmaxillary fenestrae in caenagnathid oviraptoro-saurs and therizinosauroids are considered rever-sals. The absence of both fenestrae in thesecoelurosaurs might conceivably be synapomorphicfor the oviraptorosaur-therizinosauroid clade, butthis would require the redevelopment of these samestructures in oviraptorid oviraptorosaurs.
In the analysis of HOLTZ (1994), the presence ofthe jugal participating in the margin of the internalantorbital fenestra (58.1) was hypothesized to besynapomorphic of "Maniraptora" (properly Orni-tholestes plus Maniraptoriformes: HOLTZ, 1996b). Itwas also noted to be present in the coelophysoidDilophosaurus and the abelisaurid Carnotaurus (re-sulting in a coding of "(0,1)" for this feature, Charac-ter 86, for Abel isaur idae in HOLTZ, 1994).Subsequent to that study, this condition has beenobserved in various other non-maniraptoriform taxa,including Monolophosaurus (ZHAO & CURRIE,1993), Sinraptor (CURRIE & ZHAO, 1993a), andAfrovenator (SERENO et al., 1994). It is also presentin Herrerasaurus (SERENO & NOVAS, 1994), a formthat may be the sister taxon to the ceratosaur-tetanurine clade Neotheropoda. Because of thegreater distribution of this feature than previouslyrecognized, the current analysis considers it poten-tially a neotheropod, or even a herrerasaurid plusneotheropod, synapomorphy under acceleratedtransformation.
The furcula (225.1) was once known only in de-rived coelurosaurs (BARSBOLD, 1983; GAUTHIER,1986). Its discovery in taxa more distantly related tobirds (CHURE & MADSEN, 1996; MAKOVICKY & CUR-RIE, 1998) indicates it has a much broader distribu-tion than previously realized. The clavicles are fused
to form a furcula in allosaurids and an unnamed "car-charodontosaurid" (ALCOBER et al., 1998) (neitherseparate clavicles nor fused furculae have been re-ported for other carnosaurian taxa) and various coe-lurosaurian clades, but are apparently unfusedwhere known among ceratosaurs (the neocerato-saur Carnotaurus (BONAPARTE, NOVAS & CORIA,1990); Segisaurus (CAMP, 1936)). This indicatesthat, minimally, the clavicles were fused into a fur-cula in the basalmost avetheropod (i.e., the most re-cent common ancestor o f carnosaurs andcoelurosaurs). However, as neither separate clavi-cles nor furculae have been reported among thenon-avetheropod tetanurines, it may be that thisstructure arose even more basally among theropods(see also SERENO, 1997).
The development of the sternum in theropodphylogeny has a rather perplexing distribution. Itseems to be poorly preserved in many taxa (beingrecovered in only one specimen of Archaeopteryx,for example, despite the excellent preservation ofseveral of the other specimens: WELLNHOFER,1993). In birds and in some oviraptorids (BARSBOLD,1983) the sternal plates are fused into a single me-dial element, while in dromaeosaurids (NORELL &MAKOVICKY, 1997), tyrannosaurids (LAMBE, 1917),ornithomimosaurs (PÉREZ-MORENO et al., 1994),Scipionyx (DAL SASSO & SIGNORE, 1998), and abeli-saurids (BONAPARTE, NOVAS & CORIA, 1990) there isa pair of unfused elements. The recent discovery ofsternal plates fused into a single median element(221.1) with a ventral ridge (222.1) in spinosaurids(CHARIG & MILNER, 1997) and sinraptorid carno-saurs (CURRIE & ZHAO, 1993a), similar to the condi-tion found in oviraptorids and birds, may beconvergent with these coelurosaurs. Alternatively,however, such fusion might be ontogenetically con-trolled (CURRIE & ZHAO, 1993a; CHARIG & MILNER,1997), in which case the specimens of theropodswith unfused sternals represent subadult or juvenileindividuals (an hypothesis already proposed for thetype of Scipionyx: DAL SASSO & SIGNORE, 1998).
There has been much discussion of the semilu-nate carpal block (255.1) and its significance intheropod phylogeny (OSTROM, 1969b, 1975a,1975b, 1976, 1995, 1997; BARSBOLD, 1983; GAUTH-IER & PADIAN, 1985; GAUTHIER, 1986; CHATTERJEE,1988, 1997; FEDUCCIA, 1996; PADIAN & CHIAPPE,1997, 1998; CURRIE & CARPENTER, in press). Al-though OSTROM (1969a, b) identified this structureas the radiale, PADIAN & CHIAPPE (1997, 1998) andCURRIE & CARPENTER (in press) argue that thisblock is homologous to the fusion of distal carpals 1and 2, a view accepted here. Indeed, in therizino-sauroids (BARSBOLD, 1983; RUSSELL & DONG,1993a) these bones are incompletely fused, demon-strating that this block is composed of two elements.
38
T.R. HOLTZ, JR.
Previously known only from relatively derived coelu-rosaurian forms (GAUTHIER, 1986; HOLTZ, 1994; OS-TROM, 1997), this structure is now identified incarnosaurs (Allosaurus sp., Tate Museum unpub-lished material; Acrocanthosaurus atokensis, CUR-RIE & CARPENTER, in press) and the basal tetanurineAfrovenator (SERENO et al., 1994). Based on the dis-tribution of derived character states found in thisanalysis, the sequence of transformations of thetheropod wrist can be summarized as: 1) fusion ofdistal carpals 1 & 2 among basal neotheropods, asdocumented in some (but not all) specimens of coe-lophysids (COLBERT, 1989; RAATH, 1990) and alladult tetanurine carpi except for therizinosauroids;2) development of well developed trochlea and thesemilunate shape (255.1) but the element does notcompletely cap the proximal surfaces of metacar-pals I and II, among tetanurines, as demonstrated inAfrovenator, carnosaurs, Coelurus, Scipionyx, andtyrannosaurids; 3) expansion of the semilunate car-pal block to cap the entire proximal surfaces of meta-carpals (253.2), as demonstrated in maniraptorancoelurosaurs (and separately in troodontids, if theyare arctometatarsalians); and 4) fusion of the semi-lunate carpal block and the metacarpals to form acarpometacarpus (252.1), as demonstrated in me-tornithine birds. Unfortunately, the wrist of manytheropods is incompletely known, even for other-wise well preserved and articulated specimens suchas the types of Ceratosaurus (GILMORE, 1920) andCompsognathus (OSTROM, 1978), so that it is uncer-tain exactly precisely where within the phylogenythese transformations took place. For example, thecarpus is currently unknown or undescribed for allnon-avetheropod tetanurines other than Afrovena-tor, and is only partly known in any neoceratosaur(Carnotaurus: BONAPARTE, NOVAS & CORIA, 1990).
Some specimens of tyrannosaurids and all or-nithomimosaurs lack well developed trochlear sur-faces on any of their carpals (251.1), but the mostcomplete wrists known for these taxa (e.g., Tyranno-saurus (PIN 552-1), Albertosaurus (ROM 807; CMN11315), Gorgosaurus (CMN 2120); Struthiomimus(UCMZ(VP) 1980.1), Pelecanimimus (LH 7777))demonstrate that they possessed a single large car-pal element which did not completely cap metacar-pa ls I and I I . Th is mos t l i ke ly represen tsmodifications of the stage 2 of the evolution of thetheropod carpus mentioned above, and may well beassociated with the loss or modification of more typi-cal advanced tetanurine manual function in thesetwo derived taxa, rather than derived from a "mani-raptoran"-like condition as previously hypothesized(HOLTZ, 1994). Indeed, the carpus of a subadultspecimen of the tyrannosaurid Albertosaurus sar-cophagus (CMN 11315) quite clearly demonstratesa semilunate carpal block comparable in relativesize and shape to those of Afrovenator, carnosaurs,
and basal coelurosaurs rather than the condition inoviraptorosaurs, troodontids, dromaeosaurids, orbasal birds. However, if troodontids are indeed thesister taxon to ornithomimosaurs, the distributionbecomes more problematic: either the ancestralmaniraptoriform had a large semilunate carpalblock, subsequently reduced in tyrannosaurids andlost in ornithomimosaurs, or troodontids developedan expanded semilunate carpal independently oftrue maniraptorans.
Tyrannosaurids and ornithomimosaurs alsopose a problem with regards to the distribution ofseveral other manual characters shared by Mani-raptora or its subclades and troodontids (as well asother postcranial features discussed above). Thesemight have been present in the ancestral manirapto-riforms, and subsequently lost in the derived manusof tyrannosaurids and ornithomimosaurs (HOLTZ,1994); they might have been independently derivedin maniraptorans and troodontids; or they might indi-cate a closer relationship between troodontids andthe maniraptoran taxa here rather than with tyranno-saurids and ornithomimosaurs. However, this lasthypothesis would require that the various cranial,pelvic, and hindlimb features shared by troodontids,ornithomimosaurs, and/or tyrannosaurids to haveevolved more than once, or to have been lost inManiraptora (other than Troodontidae).
GAUTHIER (1986) proposed that the absence of afourth manual digit beyond embryonic stages(257.3) was synapomorphic for Tetanurae. This hy-pothesis was supported in additional analyses (e.g.,HOLTZ, 1994). However, as Gauthier observed, afragment of bone at the proximal end of metacarpalIII in Coelurus (AMNH 619; at the time consideredassignable to Ornitholestes; see also OSBORN,1916; OSTROM, 1969b) may be a remnant of meta-carpal IV. This suggested that the fourth metacarpal(although not necessarily the fourth digit) was pres-ent in some tetanurines. The presence of metacar-pal IV in tetanurines (indeed, in avetheropods) issupported by the discovery of a probable metacar-pal IV in the sinraptorid carnosaur Sinraptor (CURRIE& ZHAO, 1993a). The relatively flattened distal end ofthis element suggests no phalanges were present(212.2). Nevertheless, if Currie & Zhao have cor-rectly identified this bone (a homology accepted bythe present author), the absence of this element inallosaurid carnosaurs and maniraptoriform coeluro-saurs is best explained by convergence. Unfortu-nately, the manus of basal carnosaurs (e.g.,Monolophosaurus) and basal coelurosaurs (Gaso-saurus, Proceratosaurus, Dryptosaurus) is un-known or incompletely known at present.
The obturator notch on the pubis (307.1) has pre-viously been used to diagnose Avetheropoda(HOLTZ, 1994). This structure is present in allo-
39
A NEW PHYLOGENY OF THE CARNIVOROUS DINOSAURS
saurids, Dryptosaurus, Ornitholestes, Coelurus,Scipionyx, Bagaraatan, and all the various manirap-toriform subclades, thus including all the tetanurinetaxa employed by GAUTHIER (1986) and allavetheropod taxa used by HOLTZ (1994). If the phy-logenetic hypothesis presented here is correct,however, it would indicate that this opening is not asynapomorphy of Tetanurae or Avetheropoda, butwas instead independently derived in allosauridsand advanced coelurosaurs (SERENO et al., 1994,1996). The basal carnosaur Monolophosaurus re-tains an obturator foramen (307.0) (and thus lacksan obturator notch) (ZHAO & CURRIE, 1993), as dothe sinraptorids Yangchuanosaurus (DONG, ZHOU &ZHANG, 1983) and Sinraptor hepingensis (GAO,1992). It is not apparent whether the lack of contactbetween bone ventral to the obturator foramen ofSinraptor dongi (CURRIE & ZHAO, 1993a) representsan incipient obturator notch, a pathological condi-tion, or simply a matter of post-mortem damage. Fur-thermore, the pubis of the basalmost coelurosauriantaxon in this analysis, Gasosaurus, retains the obtu-rator foramen and thus lacks an obturator notch. Themost parsimonious explanation of the distribution ofthis character state in the present analysis is that itevolved independently in allosaurid carnosaurs andin advanced coelurosaurs.
As mentioned above, opisthopuby (309.3) isminimally synapomorphic for Eumaniraptora (dro-maeosaurids plus birds). Curiously, although articu-lated dromaeosaurid remains indicate that theseforms were fully opisthopubic (NORELL & MAKO-VICKY, 1997) like metornithine birds, basal avialianssuch as some specimens of Archaeopteryx (WELLN-HOFER, 1993), and the type and only specimens ofUnenlagia (NOVAS & PUERTA, 1997) and Rahonavis(FORSTER et al., 1998) had pubes which were verti-cally oriented rather than fully retroverted (309.2).Thus, either full retroversion occurred independ-ently in dromaeosaurids and metornithines, or non-metornithine avialians experienced a partial "de-retroversion" from a fully opisthopubic state. A thirdalternative, that dromaeosaurids share a more re-cent common ancestor with metornithine birds thaneither does with Archaeopteryx, Rahonavis, and Un-enlagia, is not supported by abundant derived char-acter states possessed by these latter three taxaand later birds which are not present in Dromaeo-sauridae.
In those trees where Troodontidae is consideredan arctometatarsalian, the sister clade to eumani-raptorans contains one taxon (Therizinosauroidea),which also possesses a fully retroverted pubis. It isthus possible (under accelerated transformation)that opisthopuby is ancestral for the oviraptorosaur-therizinosauroid-eumaniraptoran clade. If this werethe case, the propubic condition in Microvenator and
o v i r a p t o r o s a u r s w o u l d r e p r e s e n t a " d e -retroversion".
The obturator process of the ischium (322.1-2,323.1-2) had been hypothesized by GAUTHIER(1986) to be synapomorphic for Tetanurae, and byHOLTZ (1994) to be synapomorphic for Avethero-poda. Additionally, HOLTZ (1994) found a triangular(rather than trapezoidal) shaped obturator process(323.2) to be synapomorphic for Coelurosauria. Inthe present analysis, the distribution of these char-acter states is revised. Although the basalmost car-nosaur Monolophosaurus and the sinraptoridYangchuanosaurus lacks an obturator process (re-taining, instead, the primitive state of an obturatorflange: CHARIG & MILNER, 1997), the sister group toAvetheropoda in this analysis, Afrovenator, clearlydemonstrates this condition (SERENO et al., 1994).The basalmost coelurosaur in the present study forwhich pelvic material is known, Gasosaurus, has acarnosaur- or Afrovenator-like trapezoidal obturatorprocess (323.1) (DONG & TANG, 1985), but all morederived coelurosaurs have triangular structures (ex-cept for some derived birds, which lack the structurealtogether).
HOLTZ (1994) hypothesized that the loss of the is-chial foot (327.1) was a synapomorphy of Coeluro-sauria. This was in part due to inaccurate coding ofthe condition in Compsognathus: re-inspection ofthis taxon (and its sister taxon, Sinosauropteryx,coded together here as Compsognathidae) indi-cates that a small expansion of the distal tip of the is-chium is present (327.0). A similar termination of theischium is present in Scipionyx (hypothesized hereas the sister taxon to Maniraptoriformes), whileGasosaurus has a more primitive large expansion ofthe distal ischiadic tip. The distal part of the ischiumis not preserved in Dryptosaurus, Proceratosaurus,or Deltadromeus, while in Ornitholestes the ischiumdoes terminate in the point.
As discussed by HOLTZ (1994), the distal end ofthe ischium in ornithomimids also ends in a small ex-pansion, but as in those trees in this analysis wheretroodontids are considered arctometatarsalians, it ismost parsimoniously explained here as a reversal,as the immediate outgroups to this clade (Troodonti-dae and Tyrannosauridae) both possess a pointedtip. When troodontids are considered paravianmaniraptorans, however, the ornithomimid condi-tion is equally parsimoniously regarded as a rever-sal (if the tyrannosaurid condition is synapomorphicwith that in non-compsognathid maniraptorans) or aretention of the primitive condition (if the tyranno-saurid condition is independently acquired from ad-vanced maniraptorans). SERENO (1997) postulatedthat an ischium terminating in a point was synapo-morphic for a clade comprised of Tyrannosauridaeand "Maniraptora" (oviraptorosaurs, deinonycho-
40
T.R. HOLTZ, JR.
saurs (including troodontids), and birds: in fact, bythe definition of the term, tyrannosaurids would bewithin Maniraptora in his phylogeny; see PADIAN,HUTCHINSON & HOLTZ, 1999), and that this cladewas s is te r taxon to an orn i thomimosaur -therizinosauroid clade which retained a primitive is-chiadic expansion. The condition in therizino-sauroids is variable, however. RUSSELL & DONG(1993a) considered the Early Cretaceous therizino-sauroid Alxasaurus to lack a distal ischiadic point(based on two flattened strap-like elements theyconsidered to be the ischia), whereas other therizi-nosauroids show a number of different conditions: aterminal point in Enigmosaurus mongoliensis and avery slight expansion in Segnosaurus galbinensis(BARSBOLD, 1983) to a greatly expanded flange inNanshiungosaurus brevispinus DONG, 1979. Forthis reason, this character is coded as multistate(both present and absent) for therizinosauroids. De-pending on the optimization chosen, an ischiumending in a point is either basal for Maniraptorifor-mes (and thus reversed in those therizinosauroidslacking this condition) or is derived independently inoviraptorosaurs and paravians, in which case ther-izinosauroids retained the primitive distal ischiadicexpansion primitively, and those forms ending in atip represent yet another independent derivation ofthis structure.
HOLTZ (1994) postulated that all taxa possessingthe arctometatarsalian condition (377.1) (thepinched third metatarsal, possibly a specializationfor enhanced cursorial ability: HOLTZ, 1995b)formed a single clade, and thus this structure washypothesized to have arisen only a single time intheropod history. New data requires that this hy-pothesis be rejected. Abundant character evidencesupports the hypothesis that caenagnathids ("elmi-saurids" in HOLTZ, 1994) are nested in a clade oftheropods lacking the arctometatarsalian condition(see also SUES (1997) and MAKOVICKY & SUES(1998)). Although possessing a pinched metatarsalIII, caenagnathid metatarsi differ from those found intyrannosaurids and bullatosaurs in that metatarsalsII and IV do not contact each other on the plantar sur-face (373.0) (whereas these elements do contact onthe plantar surface in ornithomimids, troodontids,and tyrannosaurids, 373.1). Furthermore, the al-varezsaurid birds Mononykus, Shuvuuia, and Parvi-cursor possesses an arctometatarsalian pes evenmore "pinched" than that found in Arctometatarsaliaproper: the proximal shaft of metatarsal III is entirelylost, reducing this bone to simply the distal wedge(377.2). However, other alvarezsaurids (such asPatagonykus and Alvarezsaurus) lack a pinchedthird metatarsal (377.0). The current phylogenetichypothesis requires at least three origins of thisstructure: in caenagnathid oviraptorosaurs, in ad-vanced alvarezsaurids, and in true arctometatarsali-
ans. In trees where troodontids are considered thesister taxon to eumaniraptorans, a fourth origin ofthe pinched metatarsus is required. Other metatar-sal features shared by Caenagnathidae, mononyk-ine alvarezsaurids, and Arctometatarsalia, such asan elongated metatarsus (369.1) and metatarsalswhich have a midshaft cross section deeper cranio-caudally than wide mediolaterally (371.1), are alsofound in the coelophysoid Elaphrosaurus and thebasal coelurosaur Coelurus.
ALTERNATIVE RELATIONSHIPS BETWEENTHEROPOD CLADES
As has been noted in previous studies (HOLTZ,1994; SERENO, 1997), there can be no phylogeneticsolution for theropod interrelationships that does notresult in some homoplasy. Some of this homoplasysuggests alternative relationships to those found inthe most parsimonious trees in the present study.
Bremer support values or "decay indices" (BRE-MER, 1988; DONOGHUE et al., 1992), although of lim-ited utility in comparison between data matrices dueto their dependence on data set size (SANDERSON &DONOGHUE, 1996), were calculated for this study us-ing the AutoDecay program (ERIKSSON, 1998). Theresults are plotted on Fig. 8. A large number of nodeshave Bremer support values of 1 or 0: this is due inpart to the insecure phylogenetic position of taxaknown only from very incomplete fossils or with ahigh number of plesiomorphic character states(which can thus assume many alternative positionson the tree without greatly affecting tree metrics).For example, the highly incomplete Rahonavis canassume many positions among Avialae withoutgreatly increasing tree length.
Nevertheless several topologies were found tobe better supported. In order of increasing support,these are: monophyly of dromaeosaurids and aviali-ans to the exclusion of other theropods, the inclusionof tyrannosaurids in Arctometatarsalia, the inclusionof compsognathids in Maniraptora, the union of theoviraptorosaur-therizinosauroid and paravianclades to the exclusion of all other coelurosaurs, andthe sister group position of Troodontidae to Eumani-raptora (the latter four topologies not reflected onF ig . 8 as d rawn) ; Abe l i sau r i dae and theCeratosaurus-abelisaurid clades to the exclusion ofother ceratosaurs; Coelurosauria as composedhere and the union of Microvenator, Oviraptoridae,and Caenagnathidae to the exclusion of other thero-pods; the union of coelophysoids and neocerato-saurs to the exclusion of other theropods; and thecomposition of Tetanurae, Ornithomimosauria, thetherizinosauroid-oviraptorosaur clade, and Avialaeas found here.
41
A NEW PHYLOGENY OF THE CARNIVOROUS DINOSAURS
An additional method of comparing different treetopologies is also employed here. Using MacClade,the differences in tree length (i.e., the number of ad-ditional evolutionary steps necessary to explain thattopology compared to the most parsimonious foundhere) were evaluated for some previously sug-gested phylogenies. Although this method lackssome of the utility of more explicit search methods(such as calculations of Bremer support indices), itmay shed some insight on the relative strength ofsupport for various additional tree topologies.
For these calculations, the summary tree (Fig. 5)was used, and (in most cases) only a single OTUwas moved to the new position.
Elaphrosaurus was found here to be a basal neo-ceratosaur, closer to Ceratosaurus than to Coelo-
physis. However, placing it as a basal coelophysoid(i.e., as the sister taxon to node C) or as the sistertaxon to Coelophysidae require only one additionalstep (tree length 1405). Although Elaphrosauruswas once considered an ornithomimosaur (e.g.,GAUTHIER, 1986; OSMÓLSKA & BARSBOLD, 1990), itrequires fifty one additional steps (tree length 1455)to place this taxon as the sister group to Pelecani-mimus+Ornithomimidae.
As noted above, Neoceratosauria shares somefeatures with tetanurines not found in coelophysoidceratosaurs. BAKKER (1986) and PAUL (1988) pro-posed phylogenies (which were not, it must benoted, the result of numerical cladistic analyses) inwhich these taxa shared a more recent common an-cestor with birds than with Coelophysis. MovingNeoceratosauria to a sister group position to node Grequires eleven additional steps (tree length of1415). As a taxonomic note, the clade comprised ofthe traditional "neoceratosaurs" and Tetanuraewould be properly called "Neoceratosauria", as itwould be comprised of Ceratosaurus and all taxasharing a more recent common ancestor with thatgenus than with Coelophysis (see TABLE II). "Cera-tosauria" (i.e., Ceratosaurus and all taxa sharing amore recent common ancestor with it than with Ne-ornithes) would be comprised solely of Ceratosau-rus and Abelisauroidea, and thus Coelophysoideawould not be considered ceratosaurs. Furthermore,the node-defined taxon Neotheropoda (i.e., all de-scendants of the most recent common ancestor ofCeratosaurus and Neornithes) would become asubgroup of the stem-defined Neoceratosauria, andthe coelophysoids would not be considered neo-theropods.
NOVAS (1997b) proposed that the "carcharodon-tosaurs" Carcharodontosaurus and Giganotosau-rus were closely related to Abelisauridae. SAMPSONet al. (1998) also recognized several potential syna-pomorphies between abelisaurids and "carcharo-dontosaurids", without proposing a sister grouprelationship between the two. As noted previouslythere are abundant cranial similarities between abe-lisaurids and carcharodontosaurs as a whole, andbetween Carcharodontosaurus and Abelisaurus inparticular. Placing Carcharodontosaurus as the sis-ter taxon to Abelisauridae requires thirty eight addi-tional steps (tree length 1442), and placing it as thesister taxon to Abelisaurus requires thirty five addi-tional steps (tree length 1439). Moving Carcharo-dontosaurus+Giganotosaurus to a sister grouprelationship with either Abelisauridae as a whole orAbelisaurus in particular both require forty ninemore steps than the most parsimonious tree (treelength 1453).
SERENO et al. (1994) proposed "Torvosauroidea"(later emended to "Spinosauroidea": OLSHEVSKY,
42
T.R. HOLTZ, JR.
Fig. 8 - Bremer support ("decay indices") for the mostparsimonious trees found in this analysis. Only valuesgreater than one are shown. Calculations made usingAutoDecay (ERIKSSON, 1998), employing the summarycladogram (Fig. 5), but shown here on the strict consensusof all twenty most parsimonious trees (Fig. 3). Not shownhere due to polytomies on the consensus are a score oftwo each for nodes V, W, cc, ee, ff, and jj.
1995; SERENO et al. (1996, 1998)) in which the "tor-vosaurids" (Torvosaurus and Eustreptospondylus)and spinosaurids formed their own clade outside ofall other theropods. CHARIG & MILNER (1997) exam-ined several of the alleged synapomorphies of thistaxon, and found them to be wanting in Baryonyxand other spinosaurids. Other features proposed forthis grouping were discovered, in the present analy-sis, to be basal tetanurine characters lost in someadvanced subclades. Restoring Spinosauroideawith the ingroup topology as in SERENO et al. (1998)to a sister group relationship to Piatnitzkysau-rus+(Afrovenator+Avetheropoda) requires onlyseven additional steps (tree length 1411). As theanatomy of some of these taxa (such as Eustrepto-spondylus) becomes better known, new support forthis clade might be found.
Although the relatively unspecialized "megalo-saur"-grade tetanurines were found to lie outside ofAvetheropoda in this study, it requires only five addi-tional steps to place Afrovenator as a basal carno-saur (tree length 1409) and only six to placeMegalosaurus in that position (tree length 1410).
ELZANOWSKI & WELLNHOFER (1993) and MAR-TILL et al. (1996) suggested that spinosaurid dino-saurs (or some member taxon thereof) were closelyrelated to bullatosaurian coelurosaurs, primarily oncranial and dental features. Moving Spinosauridaeto a sister group position with Bullatosauria requiresthirty three additional steps (tree length 1437); fortrees where troodontids are considered paravians, itrequires thirty four additional steps to place spino-saurids as the sister taxon to Ornithomimosauria(tree length 1438). Although the highly apomorphicspinosaurids were found to be the basalmost branchof Tetanurae in this study, this position is not stronglysupported. Alternative topologies including Spino-sauridae within Avetheropoda as either a basal coe-lurosaur (sister taxon to node U) or a basalcarnosaur (sister taxon to node O) require onlyseven or six extra steps (tree lengths 1412 and 1411,respectively). Similarly, placing Spinosauridae asthe sister group to Avetheropoda requires seven ad-ditional steps (tree length 1412), and as the sistergroup to the Afrovenator-avetheropod clade re-quires only six additional steps (tree length 1411).As with most Cretaceous theropod lineages, spino-saurids are highly specialized and as-yet undiscov-ered basal members of this taxon would greatly aidin more strongly establishing their relationship.
Because its skeletal material is so abundant, andthe osteology is well known, Allosaurus has servedas an outgroup for studies of coelurosaurian rela-tionships (e.g., PÉREZ-MORENO et al., 1994; FOR-STER et al., 1998; MAKOVICKY & SUES, 1998).However, as discussed above, many of the charac-ters previously used as synapomorphies between
Allosaurus and coelurosaurs (such as the obturatornotch or the loss of metacarpal IV) are shown here tobe convergent between advanced allosaurid carno-saurs and advanced coelurosaurs. Placing Allo-sauridae (node Q) as the sister group to the moreadvanced coelurosaurs (all those closer to birdsthan to Gasosaurus) requires fourteen additionalsteps (tree length 1418). Osteological data from Al-losaurus alone should therefore be used with somecaution as an outgroup for coelurosaurian studies:data from the better described of the more primitivecarnosaurs (e.g., Sinraptor and Monolophosaurus)should also be considered in future analyses.
In those studies in which Tyrannosauridae iscoded as its own OTU, it has been found to share amore recent common ancestor with birds and othertypical coelurosaurs than with Allosaurus (Fig. 1).However, tyrannosaurids were found to occupy sev-eral possibly different positions within Coelurosau-ria in these different studies. PÉREZ-MORENO et al.(1994) and MAKOVICKY & SUES (1998) placed tyran-nosaurids as the sister group to Maniraptoriformes.This topology is eleven steps longer than the mostparsimonious trees (tree length 1415). Although nopost-Gauthier study has found tyrannosaurids toshare a more recent common ancestor with Allosau-rus than with birds, placing the tyrant dinosaurs asthe sister taxon to Allosauridae requires forty six ad-ditional steps (1450), as the sister to the Acrocan-thosaurus plus (Carcharodontosaurus+Giganoto-saurus) clade requires forty eight additional steps(tree length 1452), and as the sister taxon to Acro-canthosaurus requires fifty one extra steps (treelengths 1455).
Although troodontids have been universally re-garded as coelurosaurs (Fig. 1), the position of thisclade, too, has varied from analysis to analysis. Inparticular, troodontids share many derived featureswith avialians, dromaeosaurids, therizinosauroids,oviraptorosaurs, and various combinations thereofnot present in Tyrannosauridae or Ornithomimosau-ria. GAUTHIER (1986) considered troodontids a priorito be the sister taxon of Dromaeosauridae withinDeinonychosauria, a position found in the studies ofSERENO (1997) and MAKOVICKY & SUES (1998).This requires ten extra steps (tree length 1414).FORSTER et al. (1998) found troodontids to be basalavialians (i.e., closer to Archaeopteryx and laterbirds than to Dromaeosauridae), a position requiringonly nine steps more than the most parsimonious(tree length 1413).
Troodontids also share numerous characterswith Therizinosauroidea and Oviraptorosauria (asmentioned in RUSSELL & DONG, 1993a). PlacingTr o o d o n t i d a e a s t h e s i s t e r g r o u p t o t h etherizinosauroid-oviraptorosaur clade (node gg) re-quires only one additional steps more than the most
43
A NEW PHYLOGENY OF THE CARNIVOROUS DINOSAURS
parsimonious (tree length 1405), and is thus a veryserious candidate for a potential position for thistaxon in future studies. Placing troodontids as thesister group to node ff (the clade comprised of ovi-raptorosaurs, therizinosauroids, and eumanirapto-rans) requires only three additional steps (treelength 1407), and again might well be supported infuture analyses.
Therizinosauroidea has also been a problematiccoelurosaurian taxon. The study here agrees withthe conclusions of SUES (1997) and MAKOVICKY &SUES (1998) in which oviraptorosaurs are the sistertaxon to these long necked theropods. However,CLARK, NORELL & PERLE (1994) discussed featuresshared with therizinosauroids, troodontids, and or-nithomimosaurs. Moving Therizinosauroidea to aposition as the sister taxon to Bullatosauria requiresthirty one extra steps (tree length 1435). SERENO(1997) proposed a clade comprised of Ornithomi-mosauria and Therizinosauroidea. Placing therizi-nosauroids as the sister taxon to ornithomimosaursin a configuration using troodontids as manirapto-rans requires thirty four additional steps (tree length1438).
HOLTZ (1994) considered Oviraptoridae andCaenagnathidae ("Elmisauridae" in that study) to bemore closely related to Ornithomimus than to birds,and thus arctometatarsalians under the revised tax-onomy of HOLTZ (1996b). As SUES (1997) andMAKOVICKY & SUES (1998) have firmly established,a sister group relationship between Oviraptoridaeand Caenagnathidae is well supported by characterevidence, as is a therizinosauroid-oviraptorosaurclade (node gg in this study). Moving the whole cladeTherizinosauroidea+(Microvenator+Oviraptoro-sauria) to a sister taxon position with node cc (Tyran-nosauridae+Ornithomimosauria) requires twelveadditional steps (tree length 1416).
Although the taxa and characters employed inthis study and that of MAKOVICKY & SUES (1998) donot wholly overlap, a new arrangement using thepresent data matrix was employed to reconstruct asimilar topology among the advanced coelurosaurs(for their trees, see Fig. 1K). Leaving all other taxa inthe positions of the summary cladogram, the ad-vanced coelurosaurs were rearranged for the fol-lowing topology: Compsognathidae, Tyranno-sauridae, Pelecanimimus+Ornithomimidae, Orni-tholestes, and Coelurus were progressively closeroutgroups to node ff, and Troodontidae was placedas the sister group to Dromaeosauridae within Dei-nonychosauria. This topology is twenty eight steps(tree length 1432) than the most parsimonious ar-rangements found in this analysis.
Similarly, the coelurosaurian arrangement of thetree of SERENO (1997) (Fig. 1I) was also recon-
structed by similar methods. In this case, Compsog-nathidae was the sister group to a clade comprisedof an ornithomimosaur-therizinosauroid branch anda branch with tyrannosaurids and oviraptorosaursas progressively closer sister taxa to a clade con-ta in ing Deinonychosaur ia (Dromaeosaur i-dae+Troodontidae) and Avialae. This arrangementis forty two steps longer (tree length 1446) than themost parsimonious trees found in this study.
HISTORICAL DISTRIBUTION OF THEROPODCLADES
Mapping the summary cladogram (Fig. 5) ontothe stratigraphic time scale (Fig. 9, 10) demon-strates that there remain long durations in the geo-logic record where, according to the presentanalysis, certain taxa should be present but have yetto be discovered or recognized. For example, notetanurines nor neoceratosaurs have been de-scribed from the Late Triassic, although the exis-tence of coelophysoid ceratosaurs requires thatboth those former taxa must have already divergedfrom Ceratosauria and Coelophysoidea, respec-tively. Similarly, the presence of Allosaurus in theLate Jurassic requires that the divergence betweenthe Allosaurus-Neovenator and the "carcharodonto-saur" lineages must have occurred by this point intime, despite the fact that no members of the latterclade have been identified from units older than theAptian (although RAUHUT (1995) suggested thatsome isolated teeth from the Upper Jurassic Tenda-guru Group of Tanzania may be from this lineage).
Of particular importance is the recent discoveryof an alleged therizinosauroid dentary from the Sine-murian age Lower Lufeng Formation of Yunnan,China (ZHAO & XU, 1998). If confirmed, this would in-dicate that the divergence between therizino-sauroids and oviraptorosaurs, between thetherizinosauroid-oviraptorosaur clade and theparavian lineage, between advanced manirapto-rans and Compsognathidae, between Maniraptoraand Arctometatarsalia, and all further divergenceswithin coelurosaurian lines would necessarily haveoccurred by the Sinemurian (Fig. 10), if the summarycladogram of the present analysis is supported. Sia-motyrannus may document the presence of Tyran-nosauridae in the Barremian (the probable sistertaxon to this clade, Ornithomimosauria, is alreadyknown from that interval in the form of Pelecani-mimus). The tooth taxon Koparion CHURE, 1994may record the presence of Troodontidae in the Kim-meridgian Morrison Formation of Utah, extendingthe range of this taxon to the Late Jurassic. Pres-ence of possible maniraptoriforms in the Middle Ju-rassic had previously been suggested by thediscovery of iso lated dromaeosaur id- andtroodontid-like teeth from the Bathonian of England
44
T.R. HOLTZ, JR.
45
A NEW PHYLOGENY OF THE CARNIVOROUS DINOSAURS
Fig. 9 - Summary cladogram (Fig. 5) superimposed on the geochronologic time scale I: non-maniraptoriform neo-theropods. Geochronology follows GRADSTEIN et al. (1995). Solid bars, maximum known duration of suprageneric OTUs;solid ovals, approximate geochronologic position for generic or specific OTUs; arrow indicates Maniraptoriformes (Fig.10). Genusaurus and Sarcosaurus are probable ceratosaurs not used in this analysis; Cryolophosaurus is a possibleEarly Jurassic carnosaur not used in this analysis: see text for discussion. Abbreviations: Abel., Abelisaurus; Acro., Acro-canthosaurus; Carch., Carcharodontosaurus; Carno., Carnotaurus; Cryolopho., Cryolophosaurus; Drypto., Dryptosau-rus; Genu., Genusaurus; Gig., Giganotosaurus; "M.", "Megalosaurus"; Sarco., Sarcosaurus; Spinosaur., Spinosauridae.
Fig. 10 - Summary cladogram (Fig. 5) superimposed on the geochronologic time scale II: maniraptoriform coeluro-saurs. Geochronology follows GRADSTEIN et al. (1995). Solid bars, maximum known duration of suprageneric OTUs;solid ovals, approximate geochronologic position for generic or specific OTUs; gray horizontal bars, approximate geo-chronologic position for material referred to the OTU immediately above. Solid lines, divergence pattern sufficient to ex-plain branching event without early problematic specimens; dotted lines, divergence pattern necessary to accommodateproblematic early occurrences referable to the OTU. Barremian tyrannosaurid, Siamotyrannus; Sinemurian therizino-sauroid, ZHAO & XU (1998); Kimmeridgian troodontid, Koparion; Bathonian troodontid and dromaeosaurid teeth, EVANS& MILNER, 1994; METCALF & WALKER, 1994. Abbreviations: Caen., Caenagnathidae; Theriz., Therizinosauroidea.
(EVANS & MILNER, 1994; METCALF & WALKER,1994).
The data from this new analysis indicates that thechronological conclusions of HOLTZ (1994), amongothers, were premature, and that the primary diver-gences within Avetheropoda and Coelurosauriamay have been considerably earlier than the LateJurassic. Instead, presence of Monolophosaurus,Proceratosaurus, and Gasosaurus indicate a mini-mal Middle Jurassic divergence of Carnosauria andCoelurosauria. Furthermore, Early Jurassic taxapossibly referable to these clades (Cryolophosau-rus and the Yunnan "therizinosauroid", respectively)not included in the present analysis may indicatethat the primary avetheropod divergence occurredtens of millions of years early than this study indi-cates. As such, this predicts that a greater diversityof theropods (including early members of more typi-cal Late Jurassic and Cretaceous lineages) shouldbe present in Lower and Middle Jurassic formationsthan have currently been recognized.
CONCLUSION
The present study supports many of the previ-ously discovered phylogenetic relationships amongneotheropod dinosaurs. Due to the fragmentaryand/or plesiomorphic nature of non-avetheropodtetanurines and non-maniraptoriform coelurosaurfossil material, however, these regions of the phylo-genetic tree remain poorly resolved. Even for taxafor whom the anatomy is relatively well-known, suchas Troodontidae, the mosaic of derived features re-
sult in any phylogenetic position requires some de-gree of homoplasy. Identification of Middle Jurassiccarnosaurs and coelurosaurs indicate that the diver-gence between these lineages was earlier than pre-viously suggested, and renewed search for pre-LateJurassic theropod fossils (both in the field and in col-lections) may prove among the most fruitful discov-eries for resolving the phylogeny of the carnivorousdinosaurs.
ACKNOWLEDGMENTS
Many thanks are offered to the numerous peoplewho have aided me in my on-going research intheropod systematics. This text was greatly im-proved by the comments and corrections by the nu-merous individuals, both official referees and otherinterested parties, who read and reviewed thismanuscript: in particular, I wish to thank Ralph Mol-nar (Queensland Museum), Phil Currie (Royal Tyr-rell Museum of Palaeontology), Hans-Dieter Sues(Royal Ontario Museum), Scott Sampson (StateUniversity of New York - Stony Brook), and Ber-nardino Pérez-Moreno (Universidád Autónoma,Madrid) for their helpful comments. The author issolely responsible for any errors (and original con-cepts) presented herein.
ABBREVIATIONS
AMNH - American Museum of Natural History,New York City; BMNH - Natural History Museum,London; CMN - Canadian Museum of Nature, Ot-tawa, Alberta; LH - Las Hoyas collection, Museo deCuenca, Cuenca (housed in the Unidad de Paleon-tología, Universidad Autónoma de Madrid); MCZ -Museum of Comparative Zoology, Harvard Univer-sity, Cambridge, Massachusetts; PIN - Palaeonto-logical Institute, Moscow; ROM - Royal OntarioMuseum, Toronto, Ontario; RTMP - Royal TyrrellMuseum of Palaeontology, Drumheller, Alberta;UCMZ(VP) - Museum of Zoology, University of Cal-gary, Calgary, Alberta.
APPENDIX I
Morphological characters used in the present study. Multista-te characters are considered unordered unless otherwise noted.Character polarity based on outgroup comparison: see text for ex-planation. Scoring: 0 = primitive state; 1, 2, 3, 4, or 5 = derivedcharacter states.
2. Premaxillary teeth: 0, present; 1, absent, presumably cove-red with a rhamphotheca. (RUSSELL & DONG, 1993a)
3. Number of premaxillary teeth: 0, four; 1, three; 2, five; 3, se-ven; 4, six. UO
4. Premaxillary symphyseal region: 0, V-shaped in ventralview; 1, U-shaped in ventral view; 2, Y-shaped in ventral view.UO(HOLTZ, 1994)
46
T.R. HOLTZ, JR.
5. Premaxilla subnarial depth: 0, shallow to moderately deep,main body as long or longer rostrocaudally than high dorsoven-trally; 1, very deep, main body taller dorsoventrally than long ros-trocaudally. (HOLTZ, 1994).
6. Premaxilla shape: 0, short and rounded, with short nasalprocess; 1, long and pointed, with long nasal process. (GAUTHIER,1986)
7. Medial alae from premaxilla: 0, absent or separate; 1, meetin front of vomers. (RUSSELL & DONG, 1993a)
8. Maxillary process of premaxilla: 0, moderately long, prema-xilla participates broadly in ventral surface of external naris; 1, re-duced, maxilla participates broadly in ventral surface of externalnaris; 2, extremely long, extends caudally from the caudal marginof the external naris for a distance greater than the rostrocaudallength of the external naris. UO
9. External nares: 0, without marked inset of the caudal mar-gin; 1, with marked inset of the caudal margin. (SERENO et al.,1994)
10. Premaxilla/nasal contact: 0, premaxilla and nasal meetsubnarially; 1, premaxilla and nasal do not meet subnarially.
13. Rostral ramusofmaxilla:0, absent, rostrodorsal surfaceofmaxilla forms convex surface fromdorsal ramus to ventralmargin;1, present, dramatic change in curvature of rostrodorsal surface ofmaxilla rostral to dorsal ramus forming concave surface
14. Rostral ramus size: 0, absent; 1, shorter rostrocaudallythan dorsoventrally; 2, as long or longer rostrocaudally as dorso-ventrally. UO (SERENO et al., 1996)
15. Maxillary antorbital fossa: 0, approximately 10-25% of therostrocaudal length of the antorbital cavity; 1, greater than 40% ofthe rostrocaudal length of the antorbital cavity; 2, greatly reducedin size, not extendingmuch beyond the rim of the external antorbi-tal fenestra. (SERENO et al, 1994)
16. Promaxillary fenestra: 0, absent; 1, present, visible in late-ral view; 2, present, obscured in lateral view by ascending ramusof maxilla; 3, small depression in same anatomical position whichdoes not perforate the maxilla. UO (HOLTZ, 1994)
39. Rostral portion of frontals: 0, relatively square, suture withnasals forms a relatively obtuse angle or W; 1, triangular, suturewith nasals form a distinctly acute angle. (HOLTZ, 1994)
40. Frontal shape: 0, narrow or truncated rostrally, postorbitalramus projects laterally from orbital margin of frontal; 1, verybroadly exposed on skull roof, postorbital ramus does not projectabruptly laterally from the orbital margin. (HOLTZ, 1994)
41. Frontal-frontal suture: 0, unfused; 1, fused.
42. Frontal-parietal suture on dorsal surface of skull: 0, formsa relatively straight line transversely; 1, frontals separated at me-dialmost point of suture by rostral process of parietals; 2, frontalsand parietals fused, suture indistinguishable. UO
48. Postorbital ventral process:0, broader rostrocaudally thantransversely; 1, broader transversely than rostrocaudally with U-shaped cross-section. (SERENO et al., 1996)
49. Postorbital ventral process ventralmost extension: 0, dor-sal to ventral margin of orbit; 1, ventral to ventral margin of orbit.(CURRIE & CARPENTER, in press)
50. Postorbital-lacrimal contact: 0, postorbital does not con-tact lacrimal; 1, broad.
62. Infratemporal fenestra: 0, subequal or less in area of orbitin lateral view; 1, about twice as large as the area of the orbit in la-teral view. (HOLTZ, 1994)
64. Quadratojugal-squamosal contact: 0, tip of dorsal ramusof quadratojugal contacts tip of lateroventral ramus of squamosal;1, dorsal ramus of quadratojugal does not contact squamosal; 2,broad contact between dorsal ramus of quadratojugal and latero-ventral ramus of squamosal. UO
65. Articulations of quadrate and squamosal: 0, quadrate arti-culates only with squamosal and the latter bone contacting boththe quadratojugal and postorbital; 1, quadrate articulates withboth prootic and squamosal, and the latter contacting neither thequadratojugal nor the postorbital. (CHIAPPE, NORELL & CLARK,1996)
67. Quadrate foramen: 0, large and situated between quadra-te and quadratojugal; 1, reduced or absent; 2, small and enclosedwithin dorsal ramus of quadrate. UO
68. Quadrate dorsal ramus: 0, less than height of orbit; 1, gre-ater than height of orbit.
69. Depth of quadrate articulation:0, level with ventral surfaceof maxilla in lateral view; 1, projects well ventral of the ventral sur-face of the maxilla. (HOLTZ, 1994)
70. Length of quadrate articulation: 0, only slightly caudal tothe caudal point of occipital condyle in dorsal view; 1, projects wellcaudal to the caudal point of the occipital condyle;2, rostral to cau-dal point of occipital condyle. UO
71. Quadrate pneumaticity: 0, absent or poorly developed; 1well developed.
72. Secondary palate: 0, primarily soft; 1, well ossified frompremaxilla through one-half the length of the ventral surface of themaxilla.
73. Vomera: 0, separate rostrally; 1, fused rostrally.(GAUTHIER, 1986)
74. Vomer length: 0, limited to rostral region; 1, extends cau-dally to basicranium. (RUSSELL & DONG, 1993a)
80. Subsidiary fenestra between pterygoid and palatine: 0,absent; 1, present. (GAUTHIER, 1986)
81. Ventral ectopterygoid recess: 0, absent; 1, present andcomma-shaped; 2, present and subcircular. UO (SERENO et al.,1996)
82. Endocranial cavity: 0, typical size of other bipedal dino-saurs; 1, enlarged relative to other dinosaurs, but temporal mus-culature extends origin onto frontals;2, greatly enlarged, temporalmusculature fails to extend origin onto frontals. O (GAUTHIER,1986)
83. Nuchal crest: 0, small or absent; 1, pronounced. (HOLTZ,1994)
84. Supraoccipital with very pronounced, strongly demarca-ted median ridge: 0, absent; 1, present.
87. Paroccipital processorientation:0, occipital surfaceof dis-tal end oriented more caudally than dorsally; 1, conspicuous twistin the distal end orients distal surfacemore dorsally than proximalregion; 2, curving ventrally and pendant. UO (CURRIE, 1995)
88. Basicranium pneumatization: 0, minimal to moderate, butno expansionof basisphenoid;1, basisphenoid, but not parasphe-noid rostrum, strongly expanded and pneumatized. (RUSSELL &DONG, 1993a)
90. Number of tympanic recesses: 0, two or fewer; 1, three.(MAKOVICKY & SUES, 1998)
91. Branches of internal carotid artery entering hypoglossealfossa: 0, enter separately; 1, enter through single common fora-men. (MAKOVICKY & SUES, 1998)
99. Exoccipital-opisthonic caudoventral limit of contact withbasisphenoid separated from basal tubera by notch: 0, absent; 1,present. (CURRIE & CARPENTER, in press)
100. Basipterygoid processes: 0, moderately long, not fusedto pterygoids; 1, very short, not fused to pterygoids; 2, very short,fused to pterygoids. UO (RUSSELL & DONG, 1993a)
112. Dentary caudal depth: 0, subequal to 120%depth of den-tary symphysis;1, 150-200%depth of dentary symphysis;2, grea-ter than 220% depth of dentary symphysis.
113. Rostral surangular foramen:0, absent or very small pit;1,larger, in rostrally-oriented depression.
114. Caudal surangular foramen: 0, small pit; 1, large ope-ning. (HOLTZ, 1994)
115. Rostral ramus of surangular: 0, shallow; 1, deep.(GAUTHIER, 1986)
116. Horizontal shelf on lateral surface of surangular, rostraland ventral to the mandibular condyle: 0, absent or faint ridge; 1,prominent and extends laterally; 2, prominent and pendant. UO
117. Rostral prong of angular: 0, does not penetrate the den-tary-splenial cavity; 1, penetrates the dentary-splenial cavity.(BAKKER, WILLIAMS & CURRIE, 1988)
119. Splenial: 0, obscured or only slightly visible in lateralview; 1, extensive triangular exposure in lateral view betweendentary and angular. (CURRIE, 1995)
120. Splenial with notch on rostralmargin of internalmandibu-lar fenestra: 0, absent ; 1, present. (SERENO et al., 1996)
123. Retroarticular process of articular: 0, faces dorsocau-dally; 1, faces caudally. (SERENO et al., 1994)
124. Retroarticular process shape: 0, short and deep; 1, elon-gated and tapering. (CURRIE, GODFREY & NESSOV, 1993)
125. Vertical columnar process on retroarticular process: 0,absent; 1, present. (CURRIE, 1995)
126. Number of teeth: 0, less than 100; 1, greater than 100.(PÉREZ-MORENO et al., 1994)
127. Dentary and maxillary teeth: 0, subequal in number andsize; 1, dentary teeth more numerous and smaller than maxillaryteeth. (RUSSELL & DONG, 1993a)
128. Serrations: 0, small serrations; 1, large denticles; 2, ab-sent. UO
129. Relative serration (or denticle) size of anterior and poste-rior carinae of maxillary and dentary teeth: 0, subequal; 1, posteri-or serrations much larger than anterior serrations.
146. Ventral keel on axial centrum: 0, present; 1, absent.(MAKOVICKY & SUES, 1998)
147. Cervical centra surfaces: 0, amphiplatyan or mildlyopisthocoelous; 1, markedly opisthocoelous.
148. Postaxial cervical pleurocoels: 0, absent; 1, one pair pre-sent; 2, two pairs present. O
149. Cervical epipophyseal shape: 0, rugosity on caudalzygapophyses; 1, powerfully developed and prong shaped. (RUS-SELL & DONG, 1993a)
150. Cervical epipophyseal height and orientation: 0, directedcaudolaterally and shorter than neural spine; 1, directed dorsola-terally and taller than neural spine. (HOLTZ, 1994)
155. Cervical zygapophyses direction: 0, overhang centrumparasagittally; 1, displaced laterally away from centrum in dorsalview. (MAKOVICKY & SUES, 1998)
156. Caudal cervical neural arch forms X-shape in dorsalview: 0, absent; 1, present. (MAKOVICKY & SUES, 1998)
157. Cranial cervicals: 0, subcircular in cranial view; 1, broa-der than deep on cranial surface, with reniform (kidney-shaped)articular surfaces that are taller laterally than at midline.(GAUTHIER, 1986)
158. Cranial cervical centra caudal extent: 0, level with orshorter than caudal extent of neural arch;1, extendbeyondcaudalextent of neural arch. (MAKOVICKY & SUES, 1998)
160. Midcervical centra length: 0, around twice diameter ofcranial face; 1, four times or more diameter of cranial face; 2, lessthan twice diameter of cranial face. UO
161. Midcervical centra breadth: 0, less than 20% broaderthan tall; 1, greater than 20% broader than tall. (SERENO et al.,1996)
162. Carotid process on caudal cervical vertebrae: 0, absent;1, present. (MAKOVICKY & SUES, 1998)
175. Dorsal centrum shape: 0, cylindrical, central section thi-ckness greater than 60% height of cranial face; 1, "hourglass"shaped, central section thickness less than 60% height of cranialface. (HOLTZ, 1994)
176. Dorsal centrum transversesection:0, subcircular or oval;1, wider than high. (MAKOVICKY & SUES, 1998)
185. Number of sacrals (as determined by number of verte-brae which attach to pelvic girdle): 0, two; 1, three; 2, four; 3, five;4, six; 5, more than six. O
196. Caudal transverse processes: 0, present beyond caudalXV; 1, only on caudals I-XV or fewer. (HOLTZ, 1994)
197. Transition point: 0, absent;1, in distal half of tail; 2, in pro-ximal half of tail; 3, in caudals I-IX. O (GAUTHIER, 1986)
198. Midcaudal vertebrae: 0, short prezygapophyses, extendless than one half centrum length; 1, moderate prezygapophyses,extendmore than one half but less than one centrum length; 2, ex-tremely long prezygapophyses, extend more than one centrumlength. O
199. Distal caudal vertebrae: 0, only slight interlocking,prezygapophyses extend less than one half centrum length; 1,moderately interlocking, prezygapophyses extend more than onehalf, but less than one, centrum length; 2, strong interlocking, non-ossified structures (cartilaginous extensions of prezyga-pophyses?) producing rigidity in caudals VII and distal; 3, extre-mely strong interlocking, bony extensions of prezygapophysesextending up to 12 centrum lengths; 4, pygostyle. UO
200. Distal caudal length: 0, as long as proximal caudals; 1,more than 130% length of proximal caudals; 2, markedly shorterthan proximal caudals. UO
201. Shaft of cervical ribs: 0, moderately long (two to three ti-mes centrum length) and slender; 1, extremely long (four or moretimes centrum length) and slender; 2, short (less than twice cen-trum length) and broad; 3, short (less than twice centrum length)and slender. UO
202. Uncinateprocesses:0, absent or unossified;1, ossified.
203. Medial gastral segment: 0, longer than lateral segment;1, shorter than lateral segment (NORELL & MAKOVICKY, 1997)
204. Chevron transition: 0, beyond caudal XVII; 1, betweencaudal X and XVII. (GAUTHIER, 1986)
205. Paired caudal and cranial chevron bases: 0, absent; 1,present. (SERENO et al., 1994)
206. Bridge of bone dorsal to haemal canal in distal chevrons:0, absent; 1, present.
208. Middle chevron shape: 0, gentle curvature; 1, dramaticbend in distal portion ("L-shaped"). (SERENO et al., 1994)
209. Distal chevrons with cranial and caudal projections, andmore than twice as long craniocaudally as tall dorsoventrally("boat-shaped"): 0, absent; 1, present. (HOLTZ, 1994)
217. Coracoid shape: 0, craniocaudally elongate to subcircu-lar; 1, ventral coracoidal process well developed; 2, subrectangu-lar, dorsoventral depth more than 130% of craniocaudal width; 3,strut-like. UO (GAUTHIER, 1986)
218. Coracoid caudoventral process length: 0, less than twiceglenoid diameter; 1, more than twice glenoid diameter. (CHIAPPE,NORELL & CLARK, 1996)
226. Forelimb (humerus + radius + manus)/hindlimb (femur +tibia + pes) length ration:0, less than 50%; 1, greater than 50%butless than 120%; 2, greater than 120%. O (GAUTHIER, 1986)
227. Forelimb/presacral vertebral series length ratio: 0, lessthan 75%; 1, greater than 75% but much less than 200%; 2, about200% or more. O (GAUTHIER, 1986)
228. Manus/pes length ratio: 0, much less than 100%; 1, grea-ter than 100%.
229. Humerus/scapula length ratio: 0, greater than 65%; 1,less than 65%. (PÉREZ-MORENO et al., 1993)
230. Humerus/ulna length ratio: 0, greater than 100%; 1, lessthan or equal to 100%.
231. Ulna/femur length ratio: 0, greater than 27%; 1, less than27%. (SERENO et al., 1996)
232. Radius/humerus length ratio: 0, less than 75% but grea-ter than 50%; 1, less than 50%; 2, greater than 76%. UO
233. Manus/(humerus+ radius) length ratio: 0, less than 66%;1, greater than 66%. (GAUTHIER, 1986)
236. Humeral head: 0, low and confluent with deltapectoraland bicipital crests; 1, offset and emarginated ventrally by groove.(MAKOVICKY & SUES, 1998)
237. Internal tuberosity (= ventral tubercle) on proximal end ofhumerus development: 0, not well differentiated; 1, well differen-tiated and angular. (RUSSELL & DONG, 1993a)
238. Internal tuberosity (= ventral tubercle) of humerus shape:0, conical; 1, craniocaudally compressed and longitudinally elon-gate.
239. Internal tuberosity (= ventral tubercle) of humerusdirecti-on: 0, projected ventrally; 1, projected proximally; 2, projectedcaudally, separated from humeral head by deep capital incision.UO (CHIAPPE, NORELL & CLARK, 1996)
240. Humeral ends: 0, little or not expanded; 1, well expan-ded, greater than 150% midshaft diameter. (PÉREZ-MORENO etal., 1993)
241. Deltapectoral crest on humerus: 0, low; 1, expanded andoffset from humeral shaft. (MAKOVICKY & SUES, 1998)
246. Shape of proximal ulnar shaft: 0, straight; 1, arched.
247. Diameter of ulnar shaft: 0, equal to or slightly thicker thanthat or radius; 1, much thicker than that of radius.
248. Ulnar distal condyle: 0, transversely compressed andcraniocaudally extended approximately at same plane of humero-ulnar flexion-extensionmovement; 1, subtriangular shaped in dis-tal view,with a dorsomedial condyle, and twistedmore than 54 de-grees with respect to the proximal end. (NOVAS, 1996)
249. Ulnar facet for radius:0, small and flat;1, transverselyex-panded and concave. (MAKOVICKY & SUES, 1998)
250. Ulnar and radial distal ends: 0, loosely joined; 1, closelyjoined, even with syndesmosis. (PÉREZ-MORENO et al., 1994)
251. Distal carpal shape: 0, cubic and well formed, with obvi-ous articular surfaces; 1, flat and discoidal, no distinct articularsurfaces. (HOLTZ, 1994)
252. Carpometacarpus: 0, absent, carpals distinct units; 1,present, carpals fused to each other and to metacarpus.
253. Distal carpal I block: 0, only overlaps base of metacarpalI; 1, does not overlap metacarpal II dorsally (does so ventrally); 2,broadly overlaps metacarpal II dorsally and ventrally. O
254. Distal carpal I: 0, unfused to distal carpal II; 1, fused todistal carpal II.
255. Semilunate carpal block fully developed with transversetrochlea: 0, absent; 1, present. (GAUTHIER, 1986)
256. Metacarpal V: 0, present, with digit; 1, present, withoutungual; 2, present, without phalanges; 3, absent. O
257. Metacarpal IV: 0, present, with digit; 1, present, withoutungual; 2, present, without phalanges; 3, absent. O
258. Metacarpal III: 0, present, with digit; 1, present, withoutungual; 2, present, without phalanges; 3, absent. O
259. Metacarpal II: 0, present, with digit; 1, absent.
260. Metacarpal I size: 0, greater than one half of metacarpalII length, but less thanmetacarpal II length; 1, one half to one thirdmetacarpal II length; 2, subequal to metacarpal II length. UO
261. Articular surface betweenmetacarpals I and II: 0, placedjust at proximal end of metacarpal I; 1, extends well into diaphysisof metacarpal I. (GAUTHIER, 1986)
262. Metacarpal II length: 0, much less than humerus length;1, about 50% or greater humerus length.
263. Metacarpal III length: 0, subequal to metacarpal II; 1,clearly shorter than metacarpal II; 2, clearly longer than metacar-pal II. UO (PÉREZ-MORENO et al., 1993)
264. Metacarpal III width: 0, not very much narrower (greaterthan 50%) than metacarpal II; 1, very much narrower (less than50%) than metacarpal II. (GAUTHIER, 1986)
265. Metacarpal III shape: 0, straight; 1, bowed laterally.(GAUTHIER, 1986)
266. Base of metacarpal III: 0, along same plane as metacar-pals I and II; 1, set on palmar surface of hand below base of meta-carpal II. (GAUTHIER, 1986)
276. Flexor tubercle of unguals: 0, well developed and proxi-mally placed;1, poorly developedanddistally placed. (PÉREZ-MO-
RENO et al., 1994)
277. Manual ungual, region palmar to ungual groove: 0, widerthan region dorsal to ungual groove; 1, palmar and dorsal regionssubequal in width. (RUSSELL & DONG, 1993a)
278. Pollex ungual size: 0, subequal to unguals of digits II andIII in size; 1, larger than other manual unguals.
279. Pollex ungual length: 0, less than three times longer thanheight of articular facet; 1, greater than three times longer thanheight of articular facet. (SERENO et al., 1996)
281. Manual unguals II and III: 0, smooth proximodistal surfa-ce; 1, small nubbin proximodistally. (RUSSELL & DONG, 1993a)
282. Manual ungual cross section: 0, generally oval, two tothree times as deep as wide; 1, blade-like, more than three timesasdeepaswide;2, subtriangular, aswideorwider thandeep.UO
304. Iliac-ischial articulation:0, larger than iliac-pubic articula-tion;1, smaller than iliac-pubicarticulation. (SERENOet al., 1994)
305. Pubic peduncle of ilium proportions: 0, more developedmediolaterally than craniocaudally; 1, more developed craniocau-dally than mediolaterally. (SERENO et al., 1994)
306. Pubic peduncle of ilium depth: 0, extends ventrally to thesame level as ischiadic peduncle; 1, extends more ventrally thanischiadic peduncle. (GAUTHIER, 1986)
307. Obturator foramen of pubis: 0, present; 1, open ventrallyto form obturator notch. (GAUTHIER, 1986)
312. Pubic blade: 0, five or less times as long as broad; 1, atleast six times as long as broad.
313. Pubic apron: 0, transversely wide and proximodistallylong, extending more than 50% of pubis length; 1, limited to distalhalf of pubis length; 2, strongly reduced transversely and restric-ted to distal 25% or less of pubic length. (NOVAS, 1996)
314. Pubic foramenperforatingpubic apron in distal half of pu-bic shaft: 0, absent; 1, present. (HARRIS, 1998)
315. Pubic boot shape: 0, absent; 1, broad triangle, anglebetween shaft and caudal portion of boot obtuse; 2, rounded, an-gle between shaft and caudal portion of boot acute; 3, boat-sha-ped (pointed cranially and caudally) in ventral view and anglebetweenshaft and caudal portionof boot acute;4, triangular (apexcaudal) in ventral view and angle between shaft and caudal porti-on of boot acute. UO (HOLTZ, 1994)
321. Ischial antitrochanter:0, small or absent; 1, large. (ROWE& GAUTHIER, 1990)
322. Obturator process shape: 0, joined to pubic articular pro-cess;1, separate, trapezoidal;2, separate, triangular.UO (HOLTZ,1994)
323. Obturator process position: 0, joined to pubic articularprocess ("obturator flange" of CHARIG& MILNER (1997)); 1, sepa-rate, proximally placed; 2, separate, distally placed; 3, absent,caudoventral margin of ischium smooth from obturator notch totip. O
52
T.R. HOLTZ, JR.
324. Ischium obturator process or flange: 0, not perforated byforamen; 1, perforated by foramen.
325. Ischial proximodorsal process just distal to iliac process:0, absent; 1, present. (NOVAS & PUERTA, 1997)
326. Semicircular scar on caudolateral surfaceof ischium, justdistal to iliac process: 0, absent; 1, present. (HOLTZ, 1994)
329. Femur shape:0, prominent sigmoid curvature (S-shapedin two planes); 1, bowed in convex arc with less pronounced sig-moidality. (GAUTHIER, 1986)
330. Femoral head angle to shaft: 0, less than 90 degrees(head directed ventrally); 1, approximately 90 degrees (head di-rected horizontally); 2, greater than 90 degrees (head directeddorsally). O (HARRIS, 1998)
334. Anterior (= lesser) trochanter: 0, absent; 1, separatedfrom femoral head by cleft; 2, nearly confluent with femoral head.UO
335. Anterior trochanter of femur shape: 0, absent; 1, conicalprominence; 2, alariform; 3, cylindrical in cross-section; 4, tro-chanteric crest (fusion of greater and anterior trochanters). UO
336. Anterior trochanter of femur position: 0, absent; 1, proxi-malmost point below femoral head; 2, proximalmost point abovedistal margin of femoral head; 3, proximalmost point extends abo-ve proximal margin of femora head. O
337. Fourth trochanter of femur: 0, developed, alariform; 1,little developed; 2, absent. O (GAUTHIER, 1986)
338. Trochanteric shelf of femur: 0, moderately developed rid-ge transversely directed; 1, well developed; 2, absent. UO (PÉ-REZ-MORENO et al., 1993)
339. Muscle scar in craniodistal region of femur: 0, absent; 1,present, non-elliptical in shape; 2, elliptical in shape. UO (PÉREZ-MORENO et al., 1993)
340. Medial epicondyle (= mediodistal crest): 0, absent orweakly developed; 1, pronounced, extends one quarter or morethe length of the femoral shaft.
341. Extensor groove in craniodistal region of femur: 0, ab-sent; 1, shallowand not conspicuous;2, deep and conspicuous.O(HARRIS, 1998)
342. Groove in lateral condyle of femur: 0, absent; 1, present.(ROWE & GAUTHIER, 1990)
343. Adductor fossaandassociatedcaudodistal crest of distalfemur: 0, present, prominent; 1, reduced or absent. (CHIAPPE, NO-RELL & CLARK, 1996)
344. Ectocondylar tuber: 0, proximodistally short, proximallyplaced; 1, proximodistally long, pronounced, and extends almostto distal end of femur.
345. Sulcus alongmedial side of base of crista tibiofibularis:0,absent; 1, present. (ROWE & GAUTHIER, 1990)
346. Cnemial process:0, projects caudally;1, arises out of thelateral surface of tibial shaft. (HOLTZ, 1994)
347. Incisura tibialis cranialis: 0, occupies less than 50% ofmedial surfaceof proximal tibia;1, occupiesmore than66%ofme-dial surface of proximal tibia. (HARRIS, 1998)
348. Lateroproximalcondyle (fibular condyle) on proximal endof tibia position: 0, large and posteriorly situated; 1, small andme-dially situated. (RUSSELL & DONG, 1993a)
349. Lateroproximal condyle of tibia development in proximalview: 0, bulge from main surface of tibia; 1, conspicuous waistingbetween body of condyle and main body of tibia.
350. Crista fibularis size: 0, absent; 1, not well developed; 2,well developed. O (PÉREZ-MORENO et al., 1993)
358. Fibular tubercle for M. iliofibularis (= "anterolateral pro-cess"):0, craniolaterallyprojecting;1, laterally projecting. (NOVAS,1996)
359. Anterior surface of distal fibula: 0, does not overlap as-cending process of astragalus cranially; 1, overlaps ascendingprocess of astragalus cranially. (ROWE & GAUTHIER, 1990)
360. Fibular distal end: 0, greater than twice craniocaudalwidth at midshaft; 1, less than twice craniocaudal width atmidshaft, and consequently astragalar cup for fibula reduced; 2,pinches out less than half-way down tibia length. O
361. Fibular fusion with distal tibia: 0, absent; 1, present.
362. Astragalar ascending process: 0, not reduced in horizon-tal dimension, proximodistally very low ("ceratosauroid conditi-on"); 1, mediolaterally reduced, craniocaudally wide andproximodistally low ("allosauroid condition"); 2, craniocadually re-duced and proximodistally tall, with dorsal margin sigmoid ("or-nithomimoid/albertosauroid condition"). O (GAUTHIER, 1986)
363. Round external fossa at base of ascending process ofastragalus: 0, absent; 1, present. (HOLTZ, 1994)
368. Tibiotarsus: 0, absent, proximal tarsals unfused with ti-bia; 1, present, astragalocalcaneum fused to tibia.
369.Metatarsusproportions:0,moderate;1, elongate relativeto most other theropods of same femur length; 2, shortened relati-ve to most other theropods of same femur length. UO (HOLTZ,1994)
371. Metatarsal cross-sectional proportions: 0, subequal orwider mediolaterally than craniocaudally at midshaft; 1, deepercraniocaudally than mediolaterally at midshaft. (HOLTZ, 1994)
372. Metatarsal V: 0, not reduced; 1, vestigial or absent.(GAUTHIER, 1986)
373. Metatarsals II and IV: 0, separated at midshaft on plantarsurface bymetatarsal III; 1, contact at midshaft on the plantar sur-face. (HOLTZ, 1994)
374. Metatarsal IV size: 0, subequal in length to metatarsal II;1, longer than metatarsal II and closer to metatarsal III in length.(HOLTZ, 1994)
53
A NEW PHYLOGENY OF THE CARNIVOROUS DINOSAURS
375. Metatarsal III dorsal surface area: 0, similar in size tome-tatarsals II and IV; 1, clearly larger than metatarsals II and IV; 2,clearly smaller than metatarsals II and IV. UO (GAUTHIER, 1986)
376. Metatarsal III dorsal surface shape: 0, elliptical end; 1,hourglass shaped; 2, dumbbell shaped (cranial and (especially)plantar surfaces expanded to slightly overlap surfaces of metatar-sals II and IV); 3, dorsal surface not exposed. UO
377. Arctometatarsus: 0, absent; 1, present; 2, present, with"proximal shaft" of metatarsal III complete pinched out above dis-tal wedge. O (HOLTZ, 1994)
378. Metatarsal I length:0, not reduced;1, reducedbut retainsphalanges; 2, absent. O (GAUTHIER, 1986)
379. Metatarsal I vertical position: 0, contacts distal tarsals; 1,placed near midpoint of metatarsal II shaft; 2, placed at distal endof metatarsal II. O (GAUTHIER, 1986)
380. Metatarsal I horizontal position:0, alongplanewithmeta-tarsals II-IV;1, plantar tomedial sideofmetatarsal II; 2, completelyreverted. O
381. Pedal digits II and IV: 0, subequal in length and shorterthan digit III; 1, digit IV larger than II and closer to III in length; 2, di-git II longer than IVandcloser to III in length.UO (GAUTHIER, 1986)
382. Pedal digit I phalanges 1+2: 0, longer than pedal digit IIIphalanx 1; 1, subequal to pedal digit III phalanx 1. (SERENO et al.,1996)
383. Pedal digit II: 0, not hyperextensible; 1, hyperextensible.(HOLTZ, 1994)
384. Pedal unguals III and IV cross-section: 0, subtriangular;1, vertically oval in cross-section. (RUSSELL & DONG, 1993a)
386. Pedal ungual II size: 0, subequal to pedal ungual III; 1, si-gnificantly longer than pedal ungual III (HOLTZ, 1994).
APPENDIX II
Data matrix used for phylogenetic analysis. Scoring: 0 = pri-mitive state; 1, 2, 3, 4, or 5 = derived character states; ? = datamis-singdue to lack of knowledgeof the particular anatomical regionofthat taxonor equivocal due to evolutionary transformationof taxon(e.g., dental characters in edentulous theropods; proportionsbetween manual digits III and II or I in didactyl theropods).
ACCARIE, H.; BEAUDOIN, B.; DEJAX, J.; FRIÈS, G.; MICHARD J.-G. &TAQUET, P. (1995) - Découverte d'un dinosaure théropodenouveau (Genusaurussisteronisn.g., n.sp.) dans l'Albienma-rin deSisteron (Alpes deHaute-Provence,France) et extensi-on au Crétacé inférieur de la lignée cératosaurienne. C.R.S.Acad. Sci. Paris, 212(2): 327-334.
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