This article was downloaded by: [University of Regina]On: 24 September 2013, At: 09:17Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,37-41 Mortimer Street, London W1T 3JH, UK

Journal of Vertebrate PaleontologyPublication details, including instructions for authors and subscription information:http://www.tandfonline.com/loi/ujvp20

Early Late Cretaceous birds from Saskatchewan,Canada: the oldest diverse avifauna known from NorthAmericaTim T. Tokaryk a , Stephen L. Cumbaa b & John E. Storer ca Eastend Fossil Research Station, Box 460, Eastend, Saskatchewan, Canada, S0N 0T0b Paleobiology, Canadian Museum of Nature, P.O. Box 3443, Station “D”, Ottawa, Ontario,Canada, K1P 6P4c Royal Saskatchewan Museum, 2340 Albert Street, Regina, Saskatchewan, Canada, S4P 3V7Published online: 24 Aug 2010.

To cite this article: Tim T. Tokaryk , Stephen L. Cumbaa & John E. Storer (1997) Early Late Cretaceous birds fromSaskatchewan, Canada: the oldest diverse avifauna known from North America, Journal of Vertebrate Paleontology, 17:1,172-176

To link to this article: http://dx.doi.org/10.1080/02724634.1997.10010961

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) containedin the publications on our platform. However, Taylor & Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of theContent. Any opinions and views expressed in this publication are the opinions and views of the authors, andare not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon andshould be independently verified with primary sources of information. Taylor and Francis shall not be liable forany losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoeveror howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use ofthe Content.

This article may be used for research, teaching, and private study purposes. Any substantial or systematicreproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in anyform to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions

Journal of Vertebrate Paleontology 17(1):172-176. March 1997© 1997 by the Society of Vertebrate Paleontology

EARLY LATE CRETACEOUS BIRDS FROM SASKATCHEWAN, CANADA: THE OLDESTDIVERSE AVIFAUNA KNOWN FROM NORTH AMERICA

TIM T. TOKARYKJ, STEPHEN L. CUMBAN, and JOHN E. STORER3'Eastend Fossil Research Station. Box 460. Eastend, Saskatchewan, Canada SON OTO;

-Paleobiology, Canadian Museum of Nature. P.O. Box 3443, Station " D" , Ottawa, Ontario, Canada KIP 6P4;3Royal Saskatchewan Museum, 2340 Albert Street, Regina. Saskatchewan, Canada S4P 3V7

ABSTRACT-Five taxa of fossil birds comprising at least 17 individuals have been discovered in a Cenomanian (earlyLate Cretaceous) nearshore marine deposit along the Carrot River. near the Pasquia Hills of Saskatchewan. Canada.More than a hundred fossils. all from a single locality. constitute the oldest and most diverse avifauna from theCret aceous of North America. Four species represent the earliest known North American Ornithurae, two of them newspecies of the bapt ornithid Pasqu iaorn is, n. gen. (Hesperornithiformes). and the other two referred to the ichthyornithidlchthyornis (Ichthyornithiformes). Pasquiaornis is more primitive than Baptornis, and its humerus and femur showresemblances to those of flying birds. A presumed enantiornithine is also present.

INTRODUCTION

The richest previously reported North American Cretaceousavifauna is from the Niobrara Chalk of Kansas (Stewart, 1990).and assemblages from New Jersey also contain abundant birdremains (Olson and Parris. 1987). Other Cretaceous birds havebeen described from scattered localities representing diversebiostratigraphic zones. The Ornithurae (usage of Martin, 1983)are the best documented group. and include the loon-like Hes­perornithiformes (Hesperomis, Baptornis, and their relatives).the tern-like Ichthyornithiformes (lchthyornis) and modembirds; Cretaceous Ornithurae are best known from the NiobraraChalk of Kansas (Coniacian to lower Campanian). Older re­cords are sparse and pre-Turonian Ornithurae have not beenreported in North America. This preliminary description ofsome of the material extends the record back significantly, intothe Cenomanian of western Canada.

Dickson Hardie of Arborfield, Saskatchewan, has for manyyears collected fossils from a locality near his farmhouse alongthe Carrot River, near the Pasquia Hills (Fig . 1). Hardie's site(SMNH locality 63E03-000l) was excavated in 1992 and 1993by the Royal Saskatchewan Museum. Regina. and the CanadianMuseum of Nature, Ottawa. In it a discontinuous bone brecciaunderlies a 3 to 5 cm bentonite layer. Sediment samples takenabove and below the bone layer contain diverse pollen, dino­flagellates, and Foraminifera typical of the late Cenomanian. D .Jarzen (pers. cornm.), Canadian Museum of Nature. identified36 taxa of dinoflagellates, 65 taxa of fern spores. bryophytes,and gymnosperm and angiosperm pollen. Several diagnostictaxa are Cenomanian marker species. D. McNeil, GeologicalSurvey of Canada, Calgary, Alberta, identified the Foraminiferaand concluded that the abundance of Verneuilinoides perplexusindicates placement in the Belle Fourche Member. Ashville For­mation (pers. comm.: see also Cumbaa et al ., 1992; Cumbaaand Tokaryk, 1993). Bloch et aI. (1993) have recently re-as­signed the Ashville Formation to the Belle Fourche Formation.Unfortunately, no articulated fossils are found at this site. Thevertebrate fauna includes sharks. bony fishes, plesiosaurs, aturtle, three vertebrae of an ornithopod dinosaur, and the birdsreported here. The fossils were probably deposited in shallowwater less than 6 m deep, near the eastern shore of the WesternInterior Seaway (Cumbaa et aI., 1992 ; Cumbaa and Tokaryk,1993), which divided North America into eastern and westernsub-continents during much of the last 30 million years of theCretaceous Period. We know little about the northern portions

of this seaway. In 1994, larger samples of bone breccia werediscovered approximately 100 km northeast of the Pasquia Hillssite and contain many more bird fossils of similar nature. Thissite was revisited in 1995 with extraordinary results. When thismaterial is prepared, a full description of all the elements fromboth sites will be given.

Institutional Abbreviations-FHSM, Fort Hays State Mu­seum, Hays, Kansas; KU, University of Kansas, Lawrence,Kansas; SMNH. Royal Saskatchewan Museum, Regina. Sas­katchewan (formerly the Saskatchewan Museum of NaturalHistory).

SYSTEMATIC PALEONTOLOGY

Class AVESOrder HESPERORNITHIFORMES Furbringer, 1888

Family BAPTORNITHIDAE American Ornithologist's Union. 1910Genus PASQUIAORNIS, gen . nov.

Etymology-Pasquia, reference to the Pasquia Hills region;ornis, bird.

Diagnosis-Differs from the only other member of the fam­ily. Baptornis, in : the trochanteric ridge of the femur is closerto the shaft; proximal end relatively less expanded laterome­dially; the intercotylar prominence of the tarsometatarsus is an­terior, overhanging the shaft, and; trochlea for digit 2 posteriorand close to the base of trochlea for digit 3.

Discussion-Though none of the specimens in this genus isarticulated, sorting by size and morphology of femora, tarso­metatarsi, and tentatively the humeri suggest two taxonomicunits. Femora of Parahesperornis (e.g., KU2287) and Hesper­ornis (Marsh, 1880) are more robust and expanded at their ar­ticulating ends, with distinctive intermuscular lines. Tarsomet­atarsi of these same two groups are unlike those of Baptornisand Pasquiaornis in that the 4th trochlea is wider distally thanthe 3rd .

PASQUIAORNIS HARDlEI, gen . et sp. nov.(Fig.2A-C)

Etymology-hardiei, after Dickson Hardie of Arborfield,Saskatchewan, who donated his collection from the type local­ity, which included some of the bird specimens.

Holotype-BMNH P20n.117, left tarsometatarsus.Paratype-SMNH P20n.60 , right femur.Referred Specimens-SMNH P2409.1, proximal end of

172

Dow

nloa

ded

by [

Uni

vers

ity o

f R

egin

a] a

t 09:

17 2

4 Se

ptem

ber

2013

TOKARYK ET AL.-CRETACEOUS BIRDS FROM SASKATCHEWAN 173

500 m

II"du", B.rJ

o

r-----,,,,,,IrJl I~u'u" " ,, ,

I '

I "I ,

, "C rrot * ' ,, ,

Riv r I "I ,I II II II I, I

I I

: . :• - • _ ° Winn peg I, - -- -- .,,,

I,.... _---

•Reg na

,..­,,,,,,,,,,,,,,,,,,,,,,,,,........ ......... ''­0-'-0

AlbrnJl

~ ,,\

\I\

\\

\\ .,'Calg ryI,..,,,,,

I,,I\, ,

I, -_ ..., ----

8~:.tb..,(/, .'.-10

.,,,,,,--'

FIGURE I. Area and locality (inset) of the Carrot River site SMNH locality 63E03-0001.

right femur; SMNH P2077.62. shaft and distal end of right fe­mur; SMNH P2409.9, proximal end and shaft of left tarso­metatarsus; SMNH P2409.49, trochlea for digits 2 and 4;SMNH P2077.IIO, SMNH P2409.11, SMNH P2487.7, proxi­mal ends and shafts of right tarsometatarsi.

Tentatively Referred Specimens-SMNH P2487.3, shaftand distal end of right humerus; SMNH P2077.125, distal endof a ?juvenile left tarsometatarsus.

Diagnosis-Internal cotyle of the tarsometatarsi deflected to­ward shaft; neck of 3rd trochlea higher anteriorly than 4th ; fe­mur small (Table 1), distal rim of head perpendicular to shaft.

PASQUlAORNlS TANKEl, sp. nov .(Fig.2D-F)

Etymology-tankei, after Darren Tanke of Drumheller, AB,the first author's first teacher of paleontology and good friend .

Holotype-SMNH P2077.63, left tarsometatarsus missing3rd trochlea and distal end of 2nd trochlea.

Paratype-SMNH P2077.108, left femur.Referred Specimens-SMNH P2077.120, left quadrate;

SMNH P2077.113, partial left coracoid; SMNH P2077.123 ,P2077 .124, P2077.127, partial pelvic elements; SMNHP2409.3, shaft and distal end of left femur; SMNH P2077.109 ,left femur; SMNH P2487.2, right femur; SMNH P2077.107 ,shaft and distal end of left femur; SMNH 2467 .3, distal end ofleft femur; SMNH P2077.116, shaft and distal end of left femur;SMNH P2467.2, shaft and distal end of right femur; SMNHP2077.IO, distal end of right femur; SMNH P2487.8, proximalend and shaft of left tibiotarsus; SMNH P2077.120, shaft anddistal end of right tibiotarsus; SMNH P2077.119, proximal endand shaft of right tarsometatarsus; SMNH P2077.79, shaft anddistal end of right tarsometatarsus; SMNH P2409.2, proximalend of left tarsometatarsus; SMNH P2077.118, proximal end ofleft tarsometatarsus; SMNH P2077.72, proximal end of righttarsometatarsus.

Tentatively Referred Specimens-SMNH P2467.8, shaftand distal end of left humerus; SMNH P2487.4, shaft and distalend of right humerus.

Diagnosis-Internal cotyla of the tarsometatarsi nearly an­terior-posterior, neck of 4th trochlea higher anteriorly than 3rd ;femur large (Table 1), distal rim of head slanted toward shaft.

DISCUSSION OF THE SKELETON OF PASQUIAORNIS

Humerus-The humeri, which we tentatively assign to thisgenus, deserve special attention and are not considered ich­thyornithiform for two reasons: 1) humeri of Ichthyornis fromthe Turonian are generally smaller than in later members of thisgenus (Fox , 1984; Lucas et al., 1982) , whereas the specimensfrom the Pasquia Hills are comparatively large; 2) the distalends are angular, whereas in Pasquiaornis lateral expansion ofthe distal end is more gradual.

In P. tankei, the ectepicondylar prominence is a low ridge,parallel to the shaft and extending farther than the external con­dyle . P. hardiei has a less well-defined external condyle andectepicondylar prominence. Again, if confirmed, Pasquiaornisappears to retain characteristics of its possible flying ancestorsthat are not seen in any other hesperornithiforms.

Femur-Absence of intermuscular lines on the femur is an­other primitive character among hesperornithiforms. Pasquiaor­nis possessed less strength in the hind legs than later hesperor­nithiforms, and may not have been capable of as powerful aque­ous and subaqueous propulsion. P. hardiei, the smaller of thetwo species, has the shortest length of femur (-26% less thanP. tankei and -46% less than Baptornis advenus). P. tankei is-14% smaller than B. advenus. Ichthyornithiforms and hespe­rornithiforms are abundant in the Pasquia Hills, and evolution­ary divergence must have occurred considerably earlier.

Tarsometatarsus-In P. hardiei, the tarsometatarsus is-37% smaller than in P. tankei, and - 36% that of B. advenus.P. tankei is slightly larger than B. advenus. The tarsometatarsus

Dow

nloa

ded

by [

Uni

vers

ity o

f R

egin

a] a

t 09:

17 2

4 Se

ptem

ber

2013

174 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 17, NO.1, 1997

FIGURE 2. A-C Pasquiaomis hardiei, gen . et sp. nov. (A) P20n.60, right femur (paratype), posterior view (maximum length 47 .5 mm , aboutX1.4) . (B) P20n.117, left tarsometatarsus (holotype), anterior view (maximum length 54 .0 mm , about X1.38). (C) P2487.3, shaft and distal endof right hum erus, palmar view (maximum length 30 .5 mm, about X 1.84). D-F, P. tankei, sp . nov . (D) P2077.108, left femur (paratype), posteriorview (maximum length 64 .5 mm, about X 1.05) . (E) P20n.63 , left tarsometatarsu s (holotype), anterior view (maximum length 85 .6 mm , aboutXO.81) . (F) P2487.4, shaft and distal end of right humerus, palmar view (maximum length 41.5 mm , about X 1.63) . All above specimens werecoated with ammonium chloride. (G) Ichthyomis sp . A, P20n.67, partial left coracoid, dorsal view (maximum length 40.0 mm, about X 1.69).(H) Ichthyomis sp. B., P20n.lll, partial right coracoid, dorsal view (maximum length 14.8 rnm, about X2 .9) . 1-J, SEM photograph s of Enan­tiornithine?, P20n.66, outer metatarsal. (I) dorsal view (maximum length 12.6 mrn, about X6.4) . (J) dorso-distal view (maximum length of distalend 2.9 mm, about X 13.1).

of Pasquiaornis was also compared with the "Enaliornis-like"specimen from the Lincoln Limestone Member, Greenhorn For­mation (Cenomanian) of Kansas (FHSM VP 6318 ; Martin,1983), which differs in the presence of proximal foramina, moresharply defined external cotyla, and reduction of the intercotylarprominence. Pasquiaornis cannot be closely related to theGreenhorn taxon.

Quadrate-The quadrate of Pasquiaornis is apneumatic, and

has a fossa near the angled base of the orbital process as inother hesperornithiforms (Witmer, 1990) .

We have yet to compare the Saskatchewan material with thatof the Albian Enaliornis from England. Martin and Tate (1976)suggested close relationships between Enaliornis and hesperor­nithiforms, but a recent study of the brain case of Enaliornis"places a caveat on the hypothesis" (Elzanowski et al., 1991:105).

Dow

nloa

ded

by [

Uni

vers

ity o

f R

egin

a] a

t 09:

17 2

4 Se

ptem

ber

2013

TOKARYK ET AL.-CRETACEOUS BIRDS FROM SASKATCHEWAN 175

TABLE I. Measurements of the femora and tarsometatarsi of Pasquiaornis gen . nov. and Baptornis (Martin and Tate, 1976). Asterisk denotesestimate; TMT = tarsometatarsus.

Pasquiaornis tankei

FEMUR

TMT

LengthDiameter of headDiameter of distal articulationAntero-posterior diameter of mid-shaftTransverse diameter of mid -shaftDiameter of proximal endLengthProximal antero-posterior diameterProximal widthDistal widthTip of trochlea 2 to distal end

Pasquiaornis hardiei

P2077.60 P2077.117 P2077 .108

47 .5 64 .57.3 8.5

16.5 21.88.8 11.36.3 10.2

14.8 10.554 .0

6.19.5

7.4

P2077 .63

85 .613.016.015.0*

BaptornisadvenusKU2290

75 .011.726.012.511.028 .084*13.518.016.012.0

Order ICHTIIYORNITHIFORMESFamily ICHTHYORNITHIDAE

Genus !CHTHYORNIS

Discu ssion-Two species of !chthyornis, hereafter assignedto species A and species B, occur in the Pasquia Hills avifauna.We have not attempted to revise lchthyornis, the sole NorthAmerican genus of Ichthyorniformes, even though current tax­onomy is unsatisfactory (Olson, 1985 ; Parris and Echols, 1982).The material assigned to Ichthyornithiformes from Russia andadjacent regions (Nessov, 1992) is too fragmentary for com­parison. The Pasquia Hills records are several million yearsolder than the earliest previously known !chthyornis, from theTuronian of Alberta and New Mexico (Fox, 1984 ; Lucas et al.,1982) .

Both species are referred to !chthyornis on the basis of thecoracoid scap ular facet nearly parallel to the sternal end of theglenoid facet (Marsh, 1880) and are quite unlike hesperornithi­forms (see Martin and Tate, 1976 : fig. 9c) . A partial radi us,SMNH P2077.71 , is assigned to this genus without further spe­cific designation.

!CHTHYORNIS species A(Fig .2G)

Refer r ed Specimens-SMNH P2077.67, P2077.112,P2487.5, partial left coracoids; SMNH P2077.II, partial rightcoracoid.

Comment-The less robust of the two species, with a roundscapular facet . All three specimens are close in size of glenoidfacet and diameter of dorsoventral triosseal canal (Table 2).

!CHTHYORNIS species B(Fig . 2H)

Referred Specimen-SMNH P2077.111, partial right cora­coid .

TABLE 2. Measurements of lchthyornis coracoids from Pasquia HillsSaskatchewan. Asterisk denotes estimate.

lchthy-lchthyornis species A ornis

species BP2077 .67 P2077.112 P2077.11 P2077.111

Length of glenoid facet 6.5 6.5* 6.7 7.0Width of glenoid facet 3.5 3.3 3.1 3.9Maximum diameter of

scapular facet 3.0 3.4 2.9 3.5Dorso-ventral diameter

of triosseal cannal 7.2 7.2 7.2 8.7

Comment-Robust element (Table 2), with angular scapularfacet .

Infraclass ENANTIORNITHES?(Fig . 21, J)

Referred Specimen-SMNH n077 .66, a probable outermetatarsal.

Discussion- A member of the infraclass Enantiornithes maybe represented by a hollow, asymmetrical shaft with a distalarticulating surface. Examination of the fish debris from the siteshows no similarity to this specimen, and we are led to rulethis group out as a possibility. One side of the shaft is bluntlaterally, suggesting the articular surface of the third metatarsal.Only the very primitive A rchaeopteryx. and Sinornis and theEnantiornithes have distally unfused metatarsals (Martin, 1983;Sereno, et al., 1992).

Walker (1981) erected the avian subclass Enantiornithesbased on several skeletons from Argentina, probably Maastrich­tian in age . Martin (1983) suggested that this group should beregarded as an infraclass under the subclass Sauria. Reexami­nation and new discoveries, reported by Chiappe (1992) haveexplored some of the interrelationships of several enantiorni­thines and suggest that this avian group was a more significantelement in the faunas of the Late Cretaceous than had beenrealized. In regard to the Pasquia Hills assemblage, however,we can state only that a bird, not referable to the Ornithurae,possibly an enantiornithine, was part of the avifauna. If this isconfirmed with other discoveries, it would supplement thegroup's earlier Cretaceous fossil record and would place it un­questionably in an Ornithurae-dominated fauna, a combinationnever before recorded.

OTHER AVIAN ELEMENTS

Unidentified avian elements in the Pasquia Hills fauna in­clude four fused vertebrae of the synsacrum, the proximal endof a right carpometacarpus, several coracoids, as well as manybroken, hollow bones that can not be associated with other taxa.Three pelvic elements are known and based on the size of theacetabulum, may belong to Pasquiaornis.

DISCUSSION

The Pasquia Hills assemblage, composed of four, probablyfive species, is the oldest, diverse avian fauna known from asingle North American locality. Based on single elements fromwithin each species, there appear to be at least nine individualsof Pasquiaornis tankei, three of P. hardiei, three of lchthyornisspecies A, and one of lchthyornis species B. None of thesespecies is known from other avifaunas. The new baptornithid

Dow

nloa

ded

by [

Uni

vers

ity o

f R

egin

a] a

t 09:

17 2

4 Se

ptem

ber

2013

176 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 17, NO.1, 1997

Pasquiaornis sheds new light on the early evolution of hespe­rornithiforms; it retained some features characteristic of flyingbirds, and was probably a weaker diver than later members ofthe group.

It is also interesting to note that the rates of evolution forIchthyorniformes and Hesperornithiformes may have been dif­ferent if one looks at the available, accepted, avian record dur­ing the Late Cretaceous. Ichthyornithiformes may have been inrelative stasis for most of the Late Cretaceous, as indicated bythe singularity of genera (and possibly species) within thatgroup; the evolutionary pace of Hesperornithiformes may havebeen quicker as indicated by the number of genera (and pos­sibly species). Thus, the Hesperornithiformes may be especiallysensitive to shoreline fluctuation as caused by documentedtransgressive and regressive cycles in the Western Interior Sea­way. A possible enantiornithine may extend that group's NorthAmerican temporal range significantly.

In total, 16 or 17 avians were deposited at this site in thePasquia Hills. It will be interesting to see if the faunal com­ponent of the new site 100 krn northeast will remain the sameand if further clarification can be made on some of the tenta­tively assigned specimens.

ACKNOWLEDGMENTS

Our thanks to Mr. Dickson Hardie, whose effort in obtainingthe original collection is greatly appreciated. Photographic ser­vices were provided by the University of Saskatchewan, Sas­katoon, and Flying Pigment Design Studio, Pinawa, Manitoba.Indirect financial support was provided by Nature Saskatche­wan . Rick Day (Canadian Museum of Nature, Ottawa) preparedsome of the above specimens and was a major contributor tothe collecting efforts. Richard Zakrzewski (Fort Hays State Uni­versity, Hays) kindly lent the first author the Greenhorn For­mation "Enaliornis-like" specimen. Luis Chiappe (AmericanMuseum of Natural History, New York) and Larry D. Martin(University of Kansas, Lawrence) reviewed this manuscript inits various stages of development. Special appreciation is di­rected to Larry Martin who opened his collections, home, andthoughts to the first author. Our families provided precious per­sonal support.

LITERATURE CITED

Bloch, J., C. Schroder-Adams, D. A. Leckie, D. J. McIntyre, J. Craig,and M. Staniland. 1993. Revi sed stratigraphy of the lower Colo­rado Group (Albian to Turon ian) , Western Canada, Bulletin of Ca­nadian Petroleum Geology 41 :325- 348.

Chi appe , L. M. 1992. Enantiornithine tarsometatarsi and the avian af­finity of the Late Cretaceous Avisauridae. Journal of VertebratePaleontology 12:344-350.

Cumbaa, S. L. , and T. T. Tokaryk. 1993. Early birds, crocodile tears ,and fish tales : Cenomanian and Turonian marine vertebrates fromSaskatchewan, Canada. Society of Vertebrate Paleontology Con­ference [Abstract], Albuquerque, Program and Abstracts 13:3Ia­32a .

---T. T. Tokaryk, and D. M. Jarzen. 1992. Paleoecology of a lateCretaceous near shore marine environment, Pasquia Hills , Sas­katchewan. Canadian Paleontology Conference, September 25-27,Ottawa, Program and Abstract 2: II .

Elzanowski, A. , and P. M. Galton. 1991. Brain case of Enaliornis, anearly Cretaceous bird from England. Journal of Vertebrate Pale­ontology II :90-107.

Fox , R. C. 1984. /chthyornis (Aves) from the early Turonian (LateCretaceous) of Alberta. Canadian Journal of Earth Sciences 21:258-260.

Lucas, S. G., and R. M. Sullivan. 1982 . lchthyornis in the Late Cre­taceou s Mancos shale (Juan Lopez member), northwestern NewMexico. Journal of Paleontology 56:545-547.

Marsh, O. C. 1880. Odontornithes: a monograph of extinct toothedbirds of North America. U. S. Geological Explorations of the 40thParallel, Washington, D.C., Publication 7.

Martin, L. D. 1983. The origin and early radiation of birds ; pp . 291­338 in A. H. Bush and G. A. Clark, Jr. (eds.) , Perspectives inOrnithology. Cambridge University Press, Cambridge.

--- and J. Tate, Jr. 1976. The skeleton of Baptornis advenus fromthe Cretaceous of Kansas Smithsonian Contributions to Paleobiol­ogy 27:35-66.

McNeil, D. H., and W. G. E. Caldwell. 1981. Cretaceous rocks andtheir Foraminifera in the Manitoba Escarpment. Special Paper, Geo ­logical Association of Canada 21, 439 pp.

Nessov, L. A. 1992. Mesozoic and Paleogene birds of the USSR andtheir paleoenvironments; pp. 465-478 in K. E. Campbell (ed .), Pa­pers in Avian Paleontology Honoring Pierce Brodkorb. NaturalHistory Museum of Los Angeles County, Los Angele s, ScienceSeries 36.

Olson , S. L. 1985. The fossil record of birds ; pp. 79-238 in D. S.Farner, J. R. King , K. C . Parkes (eds.), Avian Biology , AcademicPress, New York.

--- and D. C. Parris . 1987. The Cretaceous birds of New Jersey.Smithsonian Contributions to Paleobiology 63:1-22.

Parris, D. C; and J. Echols. 1992. The fossil bird /chthyornis in theCretaceous of Texas. Texas Journal of Science 44:201-212.

Sereno, P., and R. Chenggang. 1992. Early evolution of avian flightand perching: new evidence from the Lower Cretaceous of China.Science, 255 :845-848.

Stewart, J. D. 1990. Stratigraphic distribution of Niobrara vertebrates;pp. 19-30 in S. C. Benn ett (ed .). Niobrara Chalk Excursion Guide­book , Society of Vertebrate Paleontology Symposium , October 9­10, University Geological Survey of Kans as, Lawrence.

Walker, C. A. 1981. New subclass of birds from the Cretaceous ofSouth America. Nature 292 :51-53.

Witmer, L. M. 1990. The craniofacial air sac system of Mesozoic birds(Aves). Zoological Journal of the Linnean Society 100:327-378.

Received 27 November /995; accepted 20 Mar ch /996.

Dow

nloa

ded

by [

Uni

vers

ity o

f R

egin

a] a

t 09:

17 2

4 Se

ptem

ber

2013