A revision of the fossil taxa assigned to Hyperaulax (Gastropoda: Odontostomidae), with the description of a new genus (Gastropoda: Bulimulidae) Kurt Auffenberg 1 John Slapcinsky Roger W. Portell Florida Museum of Natural History University of Florida P.O. Box 117800 Gainesville, FL 32611 USA ABSTRACT Orthalicoid terrestrial snails recorded from the lower Miocene portion of the upper Oligocene to lower Miocene Tampa Member of the Arcadia Formation (Hawthorn Group) of south- ern Florida and the lower Miocene St. Marks Formation of northern Florida are reviewed. These taxa, previously allocated to the genus Hyperaulax Pilsbry, 1897 (Odontostomidae), are reassigned to Tocobaga new genus (Bulimulidae) on the basis of a distinctive suite of morphological characters, particularly those of the peristome and the embryonic whorl sculpture. Examination of all type material of the fossil taxa histori- cally assigned to Hyperaulax reveals that only three species are separable (Partula americana Heilprin, 1886; Bulimulus americanus wakullae Mansfield, 1937; and Bulimus floridanus Conrad, 1846). The varietal names Bulimulus americanus var. partulinus and B. americanus var. laxus, both Dall, 1890, are indistinguishable from the nominate form in any important morphological character. Bulimulus heilprinianus, Bulimulus stearnsii, both Dall, 1890, and Bulimulus ballistae, Bulimulus remolina, Bulimulus tampae, and Bulimulus tortilla, all Dall, 1915, are synonyms of B. floridanus Conrad, 1846. The status of B. a. wakullae from northern Florida is problematic. Although clearly not conspecific with P. americana, it is ten- tatively assigned to Tocobaga new genus and is herein elevated to species level. The biogeography of Tocobaga new genus is tentatively discussed. Fossiliferous deposits in North America and South America have not yielded taxa with the combina- tion of shell characters found in the new genus and relationships with other bulimulid genera are unknown. However, it is proba- ble that the new genus, like other non-marine mollusks from the Tampa Member of the Arcadia Formation, dispersed to Florida after contact between the Caribbean Plate and the Bahama Platform (circa 38 Ma). Additional Keywords: Tocobaga new genus, Miocene, Florida INTRODUCTION Hyperaulax Pilsbry, 1897a (type species, Bulimulus ridleyi E. A. Smith, 1890) was described as a subgenus of Bulimulus Leach, 1814 (Bulimulidae Tryon, 1867) to encompass taxa having axial wrinkles on the embry- onic whorls and a distinct channel at the posterior inser- tion of the outer lip. Pilsbry (1901: 102–103) elevated Hyperaulax to genus level with the “section” Bonnanius Jousseaume, 1900 and transferred it to the then subfamily Odontostominae, but did not alter the composition of the taxon, which consisted of the extant H. ridleyi and H. ramagei (both E.A. Smith, 1890) from Fernando Noronha Island, Brazil and several upper Tampa Member (Arcadia Formation) species from the Ballast Point site in Florida. Another fossil species from the western United States, Bulimulus limnaeiformis Meek and Hayden, 1856 was tentatively transferred to Hyperaulax by Wenz (1923: 731), but is now assigned to the Viviparidae (see Henderson, 1935 for references). Bonnanius Jousseaume, 1900 is currently treated as a distinct genus (Simone, 2006; Breure and Ablett, 2012), type species B. ramagei, thus restricting Hyperaulax to its type species H. ridleyi and the Florida fossil species. The basis for the assignment of the fossil species to Hyperaulax was the striking simi- larity in shell shape, size, and peristome characters between the fossil taxa and the extant H. ridleyi and, in particular, the presence in all taxa of a narrow channel at the junction of the outer lip with the body whorl (Pilsbry, 1897b: 82; 1901: 102–103). Recently, we examined numerous specimens of Ballast Point bulimulids housed in the Invertebrate Paleon- tology Collection at the Florida Museum of Natural History (FLMNH) and all type material of Florida fossil taxa assigned to Hyperaulax. We concluded that several unnecessary names had been introduced for the Florida fossils. By comparing these fossil specimens to Hyperaulax ridleyi and the type species of all other pertinent bulimulid genera and subgenera, we find that the placement of the 1 Corresponding author THE NAUTILUS 129(2):54–62, 2015 Page 54
Transcript
A revision of the fossil taxa assigned to Hyperaulax(Gastropoda: Odontostomidae), with the descriptionof a new genus (Gastropoda: Bulimulidae)
Kurt Auffenberg1
John SlapcinskyRoger W. PortellFlorida Museum of Natural HistoryUniversity of FloridaP.O. Box 117800Gainesville, FL 32611 USA
ABSTRACT
Orthalicoid terrestrial snails recorded from the lower Mioceneportion of the upper Oligocene to lower Miocene TampaMember of the Arcadia Formation (Hawthorn Group) of south-ern Florida and the lower Miocene St. Marks Formation ofnorthern Florida are reviewed. These taxa, previously allocatedto the genus Hyperaulax Pilsbry, 1897 (Odontostomidae), arereassigned to Tocobaga new genus (Bulimulidae) on the basisof a distinctive suite of morphological characters, particularlythose of the peristome and the embryonic whorl sculpture.Examination of all type material of the fossil taxa histori-cally assigned to Hyperaulax reveals that only three speciesare separable (Partula americana Heilprin, 1886; Bulimulusamericanus wakullae Mansfield, 1937; and Bulimus floridanusConrad, 1846). The varietal names Bulimulus americanus var.partulinus and B. americanus var. laxus, both Dall, 1890, areindistinguishable from the nominate form in any importantmorphological character. Bulimulus heilprinianus, Bulimulusstearnsii, both Dall, 1890, and Bulimulus ballistae, Bulimulusremolina, Bulimulus tampae, and Bulimulus tortilla, all Dall,1915, are synonyms of B. floridanus Conrad, 1846. The statusof B. a. wakullae from northern Florida is problematic.Although clearly not conspecific with P. americana, it is ten-tatively assigned to Tocobaga new genus and is herein elevatedto species level. The biogeography of Tocobaga new genus istentatively discussed. Fossiliferous deposits in North Americaand South America have not yielded taxa with the combina-tion of shell characters found in the new genus and relationshipswith other bulimulid genera are unknown. However, it is proba-ble that the new genus, like other non-marine mollusks fromthe Tampa Member of the Arcadia Formation, dispersed toFlorida after contact between the Caribbean Plate and theBahama Platform (circa 38 Ma).
Additional Keywords: Tocobaga new genus, Miocene, Florida
INTRODUCTION
Hyperaulax Pilsbry, 1897a (type species, Bulimulusridleyi E. A. Smith, 1890) was described as a subgenusof Bulimulus Leach, 1814 (Bulimulidae Tryon, 1867) toencompass taxa having axial wrinkles on the embry-onic whorls and a distinct channel at the posterior inser-tion of the outer lip. Pilsbry (1901: 102–103) elevatedHyperaulax to genus level with the “section” BonnaniusJousseaume, 1900 and transferred it to the then subfamilyOdontostominae, but did not alter the composition ofthe taxon, which consisted of the extant H. ridleyi andH. ramagei (both E.A. Smith, 1890) from FernandoNoronha Island, Brazil and several upper Tampa Member(Arcadia Formation) species from the Ballast Point sitein Florida. Another fossil species from the western UnitedStates, Bulimulus limnaeiformis Meek and Hayden,1856 was tentatively transferred to Hyperaulax by Wenz(1923: 731), but is now assigned to the Viviparidae (seeHenderson, 1935 for references). Bonnanius Jousseaume,1900 is currently treated as a distinct genus (Simone, 2006;Breure and Ablett, 2012), type species B. ramagei, thusrestricting Hyperaulax to its type species H. ridleyi andthe Florida fossil species. The basis for the assignmentof the fossil species to Hyperaulax was the striking simi-larity in shell shape, size, and peristome charactersbetween the fossil taxa and the extant H. ridleyi and, inparticular, the presence in all taxa of a narrow channel atthe junction of the outer lip with the body whorl (Pilsbry,1897b: 82; 1901: 102–103).
Recently, we examined numerous specimens of BallastPoint bulimulids housed in the Invertebrate Paleon-tology Collection at the Florida Museum of NaturalHistory (FLMNH) and all type material of Florida fossiltaxa assigned to Hyperaulax. We concluded that severalunnecessary names had been introduced for the Floridafossils. By comparing these fossil specimens to Hyperaulaxridleyi and the type species of all other pertinent bulimulidgenera and subgenera, we find that the placement of the1 Corresponding author
THE NAUTILUS 129(2):54–62, 2015 Page 54
early Miocene fossils is best resolved by formally recog-nizing their distinctive suite of characters with a newgeneric epithet. We therefore adopt the name:
SYSTEMATIC PALEONTOLOGY
Tocobaga new genus
Diagnosis: Shell ovate to ovate-cylindrical in shape.Whorls 5.5–6; embryonic whorls approximately 1.2 –1.3,bluntly rounded and spirally striate; later whorls sculp-tured with weak to moderately strong axial riblets, spiralincised lines often present in interspaces, occasionallycrossing axial riblets; last half of body whorl slightly flat-tened behind peristome, ascending for last 0.2 whorl;sutures shallow to well-impressed. Peristome broadlyexpanded and thickened internally, often strongly thick-ened basally; inner and outer margins connected by dis-tinct parietal callus, interrupted by narrow channel atposterior insertion of outer lip; marginal palatal toothrobust, weak or lacking; when prominent, forming distinctsinus at upper insertion of outer lip, buttressed below.Aperture ovate to subquadrate in shape. Columellasimple, lacking lamellae. Umbilicus narrow, chink-like.
Type Species: Partula americana Heilprin, 1886.Ballast Point, Hillsborough Bay, Hillsborough County,Florida, upper Tampa Member, Arcadia Formation(early Miocene).
Content: Tocobaga americanus (Heilprin, 1886),T. floridanus (Conrad, 1846), and T. wakullae (Mansfield,1937).
Etymology: The name Tocobaga is derived from theTocobaga Tribe of Native Americans that, like theseextinct snails, inhabited the Tampa Bay region, albeit23 million years later. Tocobaga was first used in Spanishdocuments of the 1560s in reference to the male chiefof the group, the chief’s village, as well as the peoplethemselves. Since no gender was implied when the
name was established, we treat the genus name Tocobagaas masculine.
Discussion: The primary shell character used to dif-ferentiate many genera of Orthalicoidea Albers, 1860 isthe embryonic whorl sculpture (Pilsbry, 1895, 1896). Theefficacy of this character is supported at least in part byindependent genetic evidence (Breure and Romero, 2012).The embryonic whorl sculpture of Tocobaga americanusis microscopically spirally striate (Figure 1) while that ofHyperaulax ridleyi, the type species of that genus, is axi-ally wrinkled (Figure 2). This character alone serves toremove the fossil species from Hyperaulax. In addition,the first embryonic whorl of the Florida fossils is low,rounded with a weakly impressed suture (Figure 1), whilethat of H. ridleyi is greatly elevated, with a deeplychanneled suture (Figure 2). These features of theembryonic whorl clearly indicate that the fossil taxahave been erroneously assigned to Hyperaulax.
The early assignment of these species to the orthalicoidfamily Bulimulidae was logical given their close resem-blance in gross shell morphology to several extant bulimulidtaxa and the biogeography of the Caribbean Basin. Theonly families outside the orthalicoids that serve as rea-sonable alternatives to this arrangement on the basis ofshell morphology are the Partulidae and Enidae. In fact,Heilprin (1886) described T. americanus as a species ofPartula Ferussac, 1821, and Moellendorff (1901) sug-gested that H. ridleyi belonged to the enid genus NapaeusAlbers, 1850. Hence, the evidence for the placement ofthe fossil taxa in the Bulimulidae is examined below.
The fossil species are readily distinguished from partulidsby a variety of features. Of greatest importance arefeatures of the embryonic whorls. Both partulids andTocobaga have spirally striate embryonic whorls, but thestriae of the partulids are much coarser. The embryonicwhorls of partulids are conic and flat-sided, with barelyany relief at the suture; the embryonic whorls of Tocobagaare rounded at the periphery, more globose, and withmore distinct sutures. The later whorls of partulids aremore rapidly expanding than those of Tocobaga and the
Figures 1–2. Embryonic whorl sculpture of Tocobaga new genus and Hyperaulax. 1. Tocobaga americanus (Heilprin, 1886).UF 66651 (Invertebrate Paleontology Collection). 2. Hyperaulax ridleyi (E.A. Smith, 1890). UF 109915 (Malacology Collection).Scale bar ¼ 0.5 mm.
K. Auffenberg et al., 2015 Page 55
shells typically have an incomplete peristome lackingthe parietal callus and associated groove at the junctionof the outer lip with the body whorl that characterizesTocobaga. From these characters it can readily be seenthat the relationship of the early Miocene fossils is notwith the partulids.
Separating Tocobaga from the Enidae on the basisof shell morphology is more difficult. Many enid taxahave shell morphologies very similar to that of Tocobaga(i.e., a channel at the posterior insertion of the outerlip and an expanded peristome). Enid embryonic whorlsmay be smooth or spirally striate. The fossil genusDendropupa Owen, 1859 (see below), has axial sculptureon the embryonic whorls (Solem and Yochelson, 1979).The enid body whorl may ascend behind the peristome,but does not become flattened near the aperture as inTocobaga. The primary reason for excluding Tocobagafrom assignment in the Enidae is biogeographic. Theenids are currently restricted to Europe, northern Africa,central and southern Asia, and the Pacific from Indonesiato Melanesia. Known fossils of this family are restricted tothe same locations with the exception of Dendropupa,which has been collected from Upper Carboniferoussediments in eastern Canada, France, and Poland (Solemand Yochelson, 1979). Other enid fossils are known fromthe Paleocene of Europe and later records throughthe Tertiary of Europe, Africa, and the Middle Eastthrough Central Asia to China (Zilch, 1959). Solem andYochelson’s assignment indicates a possible Laurasianorigin for the Enidae and a distribution of Dendropupathat pre-dates the separation of North America andEurope. However, the Enidae is unknown in subsequentNorth American land snail faunas and there is no otherevidence that it constituted a component of the AmericanMiocene fauna. Thus, we agree with Pilsbry (1901) thatthe resemblance of Hyperaulax and the Florida fos-sils to certain members of the Enidae is most likelythe result of convergent adaptations to dry habitats.The thickened peristome allows for an efficient shell/substrate seal during aestivation, while the canal actsas a contact to the exterior.
The current geographic distribution of Orthalicoideaincluding the Bulimulidae strongly suggests that bulimulidscould be expected in the fossil fauna of the CaribbeanBasin, including early insular environments on theFlorida Platform. Among Orthalicoidea families, Tocobagais best assigned to the Bulimulidae. It is readily sepa-rated from the Amphibulimidae P. Fischer, 1873 (e.g.,Amphibulima de Montfort, 1810) on the basis of shellshape and degree of calcification. The fossils do notbelong with the Orthalicidae Albers, 1860 (e.g., Liguusde Montfort, 1810) because those taxa have larger,imperforate shells and a simple lip. Tocobaga cannotbe assigned to the Odontostomidae because of theelevated embryonic whorls of the latter, lacking inspiral sculpture as discussed above. In addition, mostodontostomids have apertural barriers. Hence, we agreewith earlier authors that the Florida fossil species areproperly assigned to the Bulimulidae.
The distinctively striate embryonic whorls of Tocobagadiffer from all other North American and AntilleanBulimulidae which are either axially ribbed as in BulimulusLeach, 1814 and Rabdotus Albers, 1850, or both axiallyand spirally ribbed as in Drymaeus Albers, 1850. Dall(1890) tentatively assigned all Florida taxa known atthat time to the South American group AnctusMartens,1860, based on similarities such as a laterally com-pressed body whorl behind a broadly reflected peri-stome. However, the embryonic whorls of Anctus aresmooth and lack the channeled and calloused parietalarea. Only the South American genera, LopesianusWeyrauch, 1958, Leiostracus Albers, 1850, DiscoleusBreure, 1978, and some Bostryx sensu lato Troschel,1847 possess a similarly striate embryonic whorl sculp-ture. Of these genera, Lopesianus differs from Tocobagain having fewer and stronger spiral striae on the embry-onic whorls (Weyrauch, 1958: pl. 6, figs. 8); deeplychanneled, crenulate sutures; no parietal callus; andan incomplete, simple peristome. Leiostracus differs inhaving the spiral striae confined to the lower half ofeach whorl; papilliform embryonic whorls; and anincomplete peristome only slightly expanded. Discoleusdiffers in having a larger, more bulbous embryonicwhorl; a subovate aperture; more convex whorls; and asimple, incomplete peristome.
The polyphyletic genus Bostryx sensu lato (Breureand Romero, 2012) is the most difficult genus fromwhich to distinguish Tocobaga, a reflection of the pre-sumably diverse nature of the former. In each of severalcharacters, one or a few species of Bostryx sensu latocan be found that approach the state seen in Tocobaga.However, in no case does any species of Bostryx sensulato approach the entire suite of characters that serveto distinguish the fossils from other Bulimulidae.
We examined the type species of all but two (ElatibostryxWeyrauch, 1958 and Kionoptyx Haas, 1966) of the21 generic synonyms (or subgenera) given by Breure(1979) as belonging to Bostryx sensu lato to determinewhether any of these names could apply to the earlyMiocene fossils. All but Peronaeus Albers, 1850, PlatybostryxPilsbry, 1896, Phenacotaxus Dall, 1912, ScansicohleaPilsbry, 1930, and Pampasinus Weyrauch, 1958 can bedismissed for having embryonic whorls that are entirelysmooth or having a combination of spiral and axialsculpture (the type of Bostryx sensu stricto, B. solutus(Troschel, 1847) has smooth embryonic whorls).Elatibostryxand Kionoptyx are disregarded because of their dis-similar embryonic whorl sculpture and/or shell mor-phology mentioned in the original descriptions (Haas,1966: 239; Weyrauch, 1958: 113). Peronaeus, Pampasinus,and Platybostryx can be eliminated on the basis of shellshape. The first is greatly elongated, and the other twogenera are thick and lens-shaped. Phenacotaxus, Scansicohlea,and Tocobaga have similar shell shapes, but do not agreein any other of the characters we use to distinguish thelatter. Phenacotaxus and Scansicohlea have simple peri-stomes, their body whorls do not ascend near the aper-ture and are evenly expanded, not flattened behind the
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peristome. It is clear that the morphology of Tocobaga isunique, that this taxon has no close resemblance to any ofthe name-bearing species currently synonomized withBostryx sensu lato, and that consequently, none of thesenames can serve to accommodate the Florida fossils.
Examination of the holotypes of all named fossil“Hyperaulax” indicates that only three species are recog-nizable in the Florida fossils; the taxa described by Dall(1890, 1915) are synonyms of either T. americanus orT. floridanus. Below we diagnose and discuss each spe-cies. Shell length, shell width, aperture length, and aper-ture width (Tables 1–2) were measured as describedin Crampton (1916) for similarly shaped Partula. Weuse the following institutional abbreviations: ANSP
(Academy of Natural Sciences of Drexel University),UF (Florida Museum of Natural History, University ofFlorida), USNM (National Museum of Natural History,Smithsonian Institution), and WFIS (Wagner Free Insti-tute of Science, Philadelphia).
SYSTEMATICS
Tocobaga americanus (Heilprin, 1886) newcombination(Figures 3–7, Tables 1 and 2)
Partula americana Heilprin, 1886: 115, pl. 16, fig. 60.Bulimulus (? Anctus) americanus var. partulinus Dall,
1890: 7; 1915: 26, pl. 4, fig. 12.Bulimulus (? Anctus) americanus var. laxusDall, 1890: 7;
Diagnosis: A large species of Tocobaga, 15–17 mm inheight, 6–8 mm in width; shell ovate in shape; whorlsapproximately 5.5–6.5, slightly convex; shell sculpture ofevenly spaced oblique riblets of width equal to their inter-spaces; last half of body whorl slightly flattened, ascendingfor last 0.2 whorl; aperture subquadrate; peristome witha wide, flat expansion, thickened internally throughout,almost complete, inner and outer margins connected by athickened parietal callus; a narrow channel present at pos-terior insertion of outer lip, parallel to the long shell axis;umbilicus narrow; columella simple and straight.
Holotype: WFIS 865 (Figures 3–5) Ballast Point,Hillsboro [Hillsborough] Bay, [Tampa,HillsboroughCounty],Florida, upper Tampa Member, Arcadia Formation (earlyMiocene). J. Willcox and A. Heilprin, 1886.
Remarks: Tocobaga americanus is readily distinguishedfrom T. floridanus by its larger size and more ovateshape; more rapidly expanding whorls; peristome thatis expanded along the entire outer margin; channel at
Table 1. Shell morphometrics of type specimens of nominate forms of Tocobaga. L ¼ shell length, W ¼ shell width, ApL ¼aperture length, ApW ¼ aperture width; all measurements in mm, X ¼ no measurement possible. Bold species are considered valid.
Table 2. Tocobaga americanus (Heilprin, 1886) shell mor-phometrics; L ¼ shell length, W ¼ shell width, ApL ¼aperture length, ApW ¼ aperture width; number of whorls of allmeasured fossils estimated at 6þ due to erosion of embryonicwhorls. All measurements in mm.
the posterior insertion of the outer lip that is parallel tothe main axis of the shell; and a more open umbilicus.
The holotypes of Dall’s (1890) varieties laxus (Figure 6)and partulinus (Figure 7) are indistinguishable fromtypical T. americanus in any important detail. The shellsof laxus are more slender and have stronger axial sculp-ture, while those of partulinus are even more slender.However, both are also shorter in length than typicalT. americanus and all three have identical length towidth ratios. Similarly, the length to width ratios of theaperture is also alike (Table 1). Variation among 16 unbro-ken individuals of 59 specimens in UF lots 66651, 66652,and 66653 (Table 2) include a morphological range in
shell length and width and apertural length and widththat encompasses the two varietal names and we seeno need to recognize this natural variation with formalepithets. Specimens from Wakulla County, Florida ques-tionably referred to these forms (Mansfield, 1937) werenot located.
Material Examined: Partula americana Heilprin, 1886,Holotype, WFIS 865; Tocobaga americanus (Heilprin,1886), UF 66651 (1), UF 66653 (57), USNM 111965 (1);Bulimulus americanus var. partulinus Dall, 1890, Holo-type, USNM 111970; Bulimulus americanus var. laxusDall, 1890, Holotype, USNM 111971.
Figures 3–7. Tocobaga americanus (Heilprin, 1886). 3–5. Holotype of Partula americana Heilprin, 1886. WFIS 865. 6. Holotypeof Bulimulus americanus var. laxus Dall, 1890. USNM 111971. 7. Holotype of Bulimulus americanus var. partulinus Dall, 1890.USNM 119970. Scale bar ¼ 5 mm.
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Tocobaga floridanus (Conrad, 1846) new combination(Figures 8–16, Table 1)
pl. 1, fig. 18.Bulimulus (Hyperaulax) tampaeDall, 1915: 26, pl. 1, fig. 3.Bulimulus (Hyperaulax) tortillaDall, 1915: 27, pl. 1, fig. 2.
Diagnosis: A smaller species of Tocobaga, 8.1–14.1 mmin height, 3.6–6.0 mm in width; shell ovate to ovatecylindrical in shape; whorls 5–6.5, slightly convex toflattened; embryonic whorl blunt, rounded, sculptureunknown; shell sculpture of evenly spaced oblique ribletsof width equal to their interspaces, weak spiral incised
lines occasionally present in interspaces; body whorlnot evenly expanded, last half whorl slightly flattened,ascending last 0.2 whorl; aperture oval to subquadrate;peristome expanded, thickened on inner margin alongthe columellar area, basally and along anterior halfof outer lip; inner and outer peristome connected by aparietal callus; narrow channel present at posterior inser-tion of outer lip that is deflected medially at 45� rela-tive to shell long axis; umbilicus very narrow, chink-like;columella simple and straight.
Holotype: ANSP 30607 (Figures 8–10). Ninemiles fromTampa on Hillsboro [Hillsborough] River, [HillsboroughCounty], Florida, upper Tampa Member, Arcadia Forma-tion (early Miocene). The holotype is a broken speci-men. The inadequate original text-figure apparently depictsa reconstruction.
Remarks: Bulimulus longaevus Ancey, 1881 is an unnec-essary replacement name for Bulimus floridanus Conrad,1846 (see Henderson, 1935), not B. floridanus Pfeiffer,
1857, as demonstrated by Wood and Gallichan (2008: 60).Ancey (1881: 414) erroneously stated that B. floridanusPfeiffer, 1857 was described prior to Conrad’s taxon(1846), leading Wood and Gallichan (2008) to mis-interpret Ancey’s intent. The holotypes of Dall’s spe-cies Bulimulus ballistae, B. heilprinianus, B. remolina,B. stearnsii, B. tampae, and B. tortilla while differingin size are all similar in shape (Figures 8–16) and shelllength to width and aperture length to width ratiosboth to each other and to the holotype of Bulimusfloridanus (Table 1). The holotype of Bulimulus ballistae(Figure 11) is nothing more than a rather small specimenof Tocobaga floridanus differing from that species in noobvious detail. The holotypes of Bulimulus heilprinianus(Figure 12) and Bulimulus tortilla (Figure 16) differ fromthe typical T. floridanus only in having a more pro-nounced thickening on the anterior half of the innermargin of the outer lip. The holotype of B. floridanusis not fully mature and so does not prominently exhibitthis character. The holotype of Bulimulus tampae(Figure 15) is merely a large specimen of T. floridanusand differs in no characters other than its size. The holo-type of Bulimulus remolina (Figure 13) is slightly moreelongate than typical T. floridanus and has a rather flat-tened body whorl with the sculpture largely eroded. Theholotype of Bulimulus stearnsii (Figure 14) is the mostunusual specimen examined. This specimen is quite elon-gate and large; with narrow, flattened whorls; almostlacking in shell sculpture. We believe the smooth sur-face is due to erosion, because traces of the charac-teristic ribbing of Tocobaga remain on a few surfaces,most prominently behind the aperture. The specimen’slarge size and elongate shape appear to represent oneextreme of the variation in T. floridanus. The holotype
of B. remolina and other specimens (USNM 646161)are intermediate in shape between the holotype ofB. floridanus and that of B. stearnsii, or are equally asflattened as the type of B. stearnsii, although not as large.The extreme elongation in the holotype of B. stearnsiiis partly, but not entirely, a reflection of its large size,though other large specimens of T. floridanus (e.g.,USNM 646160) are more ovate in shape. Given thecontinuum in size and shape that occurs between theholotypes of B. floridanus and B. stearnsii, and the appar-ently eroded nature of the latter’s smooth surface, webelieve the holotype of B. stearnsii represents one extremeof the morphological variation seen within T. floridanus.
Tocobaga wakullae (Mansfield, 1937) new combination(Figures 17–19, Table 1)
Bulimulus americanus wakullae Mansfield, 1937: 15:70,pl. 1, figs. 10, 13.
Diagnosis: A large species of Tocobaga, ca. 26 mm inheight, >10 mm in width; shell ovate in shape; whorlsapproximately 6.5, slightly convex; embryonic whorl blunt,rounded, sculpture unknown; later whorl sculpture of
Figures 17–19. Tocobaga wakullae (Mansfield, 1937). Holotype of Bulimulus americanus wakullae Mansfield, 1937. USNM495932. Scale bar ¼ 5 mm.
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evenly spaced axial riblets more or less parallel to shelllong axis, spiral sculpture not apparent; body whorlvery slightly flattened behind apertural lip, ascendingvery slightly for last 0.2 whorl; aperture ovate, slightlyoblique; peristome moderately reflected, but not greatlyexpanded or thickened within; parietal area with weakcallus; channel at posterior insertion of outer lip notapparent; characters of umbilical area unknown; colu-mella simple, unadorned.
Holotype: USNM 495932 (Figures 17–19). About200 yards south of Wakulla Railroad Station, WakullaCounty, Florida. External mold and cast.
Remarks: Mansfield (1937) originally placed this taxonas a subspecies of Tocobaga americanus, but it differsfrom that species in its larger shell size, in having anovate instead of subquadrate aperture, in its more inflatedshape, and in having the axial shell sculpture orientedmore nearly parallel to the long axis of the shell. Thesedifferences in shell characters lead us to conclude thatthese two taxa are separate species.
Our assignment of this taxon in Tocobaga, however,is not without reservation. Several of the diagnostic fea-tures of that genus, such as the embryonic whorl sculp-ture, the channel at the posterior insertion of the outerlip, and the nearly complete peristome, cannot be exam-ined in the holotype of B. wakullae (the only specimenavailable to us) because of its poor preservation (anexternal mold) and casting material. Collection of addi-tional material may allow assessment of these particularcharacters, whereby the generic allocation of B. wakullaemay well be revised.
Tocobaga wakullae (Mansfield, 1937) was describedfrom the “Tampa Limestone” of Wakulla County innorthwestern Florida. Although Mansfield (1937) didnot discuss the stratigraphy of the type locality, the typespecimen was probably collected from what is now con-sidered the St. Marks Formation. This formation is earlyMiocene in age (Rupert and Spencer, 1988) and approxi-mately contemporaneous with the upper Tampa Member(Arcadia Formation) of the Tampa Bay area.
Material Examined: Bulimulus americanus wakullaeMansfield, 1937, Holotype, USNM 495932, external moldand cast.
BIOGEOGRAPHY
Modern orthalicoids are particularly diverse in SouthAmerica with a few lineages in Africa, Australia, Melanesia,and New Zealand. The group appears to have a Gondwanandistribution (Herbert and Mitchell, 2009). However,the family is well represented in Mexico, Central America,and the Antilles and there are representatives of a fewgenera in temperateNorthAmerica including the bulimulidsDrymaeus and Rabdotus. Several other Antillean landsnail groups were widely distributed in North Americaduring the late Cretaceous and early Tertiary (Bishop, 1979;
Roth and Hartmann, 1998) and became restricted to theAntilles as climate cooled in the Tertiary. However, theoldest North American fossil bulimulids are the FloridaMiocene fossils reviewed here and there is yet no evidencethat bulimulids were present in North America beforethen. The oldest bulimulids are from a middle Paleocenesite in southern Brazil where the family accounts formore than 30% of fossil species diversity (Salvador andSimone, 2013). The family remains the most diversefamily in South America accounting for approximately45% of recent South American species (Simone, 2006).
Many of the Florida Tampa Member (Arcadia For-mation) land snails are similar in shell morphology toextant Antillean species (Pilsbry, 1897a; Auffenberg andPortell, 1990). Fossil species were assigned to the extantAntillean genera Plagioptycha Pfeiffer, 1855, Cepolis deMontfort, 1810, and Pleurodonte Fischer de Waldheim,1807, Gongylostoma Albers, 1850, and Cerion Roding,1798 (Dall, 1915; Mansfield, 1837). While the placementof these fossil taxa in modern genera can be questioned,the fauna surely has a degree of Caribbean affinity. TheAntillean component of the Tampa Member (24–22.5 Ma,but see Scott, 1988) species apparently dispersed overwater to Florida after contact between the CaribbeanPlate and the Bahama Platform 38 Ma (Duncan andHargraves, 1984). Reexamination of the entire faunamay provide a better understanding of its biogeography.
Relationships between Tocobaga and recent bulimulidgenera remain unknown. Fossiliferous deposits in NorthAmerica have not yielded taxa closely similar to Tocobagaand the extinct South American fossil genera, PaleobulimulusParodiz, 1949 and Itaborahia Maury, 1935, have shellmorphologies quite unlike Tocobaga (Parodiz, 1969).
ACKNOWLEDGMENTS
For donation of fossil specimens to the FLMNH thatwere used in this study, we thank S.B. Upchurch (SDII-Global), T. Estevez, and the Florida Geological Survey.For specimen loans, we thank J. Thompson and the lateW. Blow (USNM), E. Bolt (WFIS), and G. Rosenberg(ANSP). Much research during an earlier version of thisstudy was performed by Fred Kraus (Bishop Museum).Information on the Tocobaga Tribe was provided byJ. Milanich (FLMNH). Pertinent literature citations andcontemplation was offered by H. G. Lee (FLMNH). Forsharing his vast knowledge of the Orthalicoidea, A. S.H.Breure (Leiden, The Netherlands) is thanked, as is F.G.Thompson (FLMNH) for reviewing an earlier draft ofthis manuscript. Digital images of the ANSP and WFIStypes were provided by P. Callomon and A. Lawless.Reviews by A.S.H. Breure and Barry Roth providedhelpful suggestions that improved this manuscript. This isUniversity of Florida Contribution to Paleobiology 669.
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