Bryan J. Small

TECOVASUCHUS CHATTERJEEI, A NEW AETOSAUR (ARCHOSAURIA: STAGONOLEPIDIDAE) FROM THE TECOVAS FORMATION (CARNIAN, UPPER TRIASSIC) OF TEXAS

Abstract A new aetosaur, Tecovasuchus chatterjeei gen. et sp. nov., from the Upper Triassic (middle or upper Carnian) Tecovas Formation of Texas is described, based primarily on osteoderms from several individuals. The diagnosis is based on a unique suite of osteoderm characters: very wide dorsal paramedian osteoderms; a low, keel-shaped dorsal boss on the dorsal paramedians that does not reach the posterior margin of the osteoderm; a strut on the ventral surface of the dorsal paramedians; ornamentation on the dorsal paramedians with both deep pits and fainter radiating grooves; a unique strongly thickened and beveled posterior edge on the dorsal paramedians; a prominent raised anterior bar on both the dorsal paramedian and lateral osteoderms; lateral osteoderms with dorsoventrally flattened, posteriorly excavated horns, reduced, tongue-like dorsal flanges, and larger, plate-like ventrolateral flanges. The low number of diagnostic criteria for identifying aetosaur osteoderms results in mandatory splitting at the generic level. Some specimens of Tecovasuchus have been misidentified previously as Paratypothorax, suggesting that shoehorning osteoderms into previously recognized taxa may conceal greater taxonomic diversity among aetosaurs than has generally been appreciated. Specimens with multiple osteoderms assignable to a single individual are important in naming and characterizing new aetosaur taxa, and at least one complete osteoderm is usually necessary when assigning specimens to pre-existing taxa.

Plemmyradytes shintoni, gen. et sp nov., an Early Permian amphibamid (Temnospondyli : Dissorophoidea) from the Eskridge Formation, Nebraska

Abstract The fossil vertebrate localities near Humboldt, Richardson County, Nebraska, have produced a diverse assemblage of amphibians from near the Permo-Carboniferous (C-P) boundary, including at least one species of dissorophoid (described here), a trimerorhachid, juvenile and adult specimens of the dvinosaur Acroplous vorax, gymnarthrid microsaur material, numerous skeletons, skulls, and isolated vertebrae assignable to two species of the lysorophian Brachydectes, and diadectid teeth. A new genus and species of amphibamid dissorophoid, Plemmyradytes shintoni, is described from the lower half of the Permian-aged Eskridge Formation (early Asselian) near Humboldt. P. shintoni is only the second amphibamid species described from the Permo-Carboniferous midcontinent sequence in the Kansas-Nebraska region. Among amphibamids, it is set apart by the following suite of characters: (1) reduction of the lateral exposure of the palatine, (2) a long, narrow supratemporal (at least twice as long as broad) roofing the otic notch, (3) a posteriorly elongated squamosal, (4) long anterior maxillary teeth, decreasing in size posteriorly, (5) a shallow dentary with a long lateral dentary trough, and (6) dentary teeth that are slightly smaller than the maxillary teeth (approximately one-half to two-thirds as long). A cladistic analysis of 67 dissorophoid characters from 17 taxa supports a clade uniting P. shintoni with ‘Tersomius’ sp. and Micropholis stowi within a monophyletic Amphibamidae. The demonstration of evolutionary trends within the family based on the new data allows a comparison of competing phylogenetic hypotheses.

A Redescription Of Acroplous vorax (Temnospondyli: Dvinosauria) Based On New Specimens From the Early Permian Of Nebraska and Kansas, U.S.A.

Abstract The Early Permian dvinosaur temnospondyl Acroplous vorax Hotton, 1959 is redescribed based on new specimens from the Eskridge Formation of Nebraska, and an unpublished specimen collected from the Speiser Shale of Kansas in 1960, along with reanalysis of previously described Acroplous specimens. The Nebraska Acroplous specimens are part of the oldest Permian (Asselian) nonmarine vertebrate faunal assemblage in the Paleozoic midcontinental sequence of the United States based upon invertebrate biostratigraphy. This study reveals previously unknown anatomical features for Acroplous, requiring a reassessment of the genus and the Eobrachyopidae. Among the new findings for Acroplous are: an anterior dorsal fenestra; prefrontals excluded from the external naris; lacrimal contacting the orbit; denticulated palatine, ectopterygoid and pterygoid; a lack of a postglenoid transverse trough; an unusual interlocking mandibular symphysis, and an elongate rod-like ilium. A cladistic analysis of 87 characters and 12 temnospondyl taxa indicates that the Eobrachyopidae (Acroplous and Isodectes) may be a paraphyletic group, with Isodectes filling a more basal position within the Dvinosauroidea.

The Cranial Morphology of a New Genus of Lungfish (Osteichthyes: Dipnoi) from the Upper Jurassic Morrison Formation of North America

ABSTRACT Much of Mesozoic diversity within the lungfishes (Osteichthyes: Dipnoi) has traditionally been relegated to the genus Ceratodus, primarily on the basis of the highly stereotypical dental plates characteristic of post-Devonian lungfishes. The new genus Potamoceratodus contains the single species P. guentheri (Marsh, 1878), comb. nov. Newly discovered material allows clarification of the features of this species, including description of a complete skull roof and partial palate. The new genus can be differentiated from the European Ceratodus on the basis of characters of the skull roof, palate, and dentition, including lack of tubercular ornamentation of the skull roof, modest convexity of the dorsal skull roof, absence of sensory sulci anteriorly in the EF bone, and an enlarged and elongate anterior odontode series on the pterygoid dental plate. The North American Ceratodus record is reexamined in light of more complete material from the Temple Canyon localities of the Morrison Formation of Colorado, USA. Ceratodus is found to be an assemblage of forms with disparate cranial morphology. The succession of North American lungfish communities in the late Paleozoic and Mesozoic is most characteristic of serial replacement rather than in situ evolution, and it is possible that the isolation of North America subsequent to the breakup of Laurentia contributed to the regional extinction of lungfishes in North America.

Cranial morphology of recumbirostrans (Lepospondyli) from the Permian of Kansas and Nebraska, and early morphological evolution inferred by micro-computed tomography

ABSTRACT ‘Microsaurs’ (Lepospondyli) were a group of tetrapods whose fossil record spanned the Mississippian—Early Permian, and have sometimes been implicated in the origins of lissamphibians (especially the fossorial caecilians). Although common in the well-sampled Permian deposits of Texas and Oklahoma, little is known of conservative recumbirostran ‘microsaurs’ from more northerly localities (Kansas/Nebraska). Data on a new, well-preserved recumbirostran, Huskerpeton englehorni, gen. et sp. nov., from the Eskridge Formation, Nebraska, reveal affinities to the purported gymnarthrid ‘Euryodus’bonneri (here moved to a new genus, Proxilodon) from the Speiser Formation, Kansas. High resolution micro-computed tomography reveals important endocranial data, including an ossified ‘supraoccipital’ that is usually absent in gymnarthrids, a dorsal sinus separating the synotic tectum from the dermal skull roof as in ostodolepids, ventral flanges of the frontals articulating directly with the ascending lamina of the sphenethmoid, and tall, ossified ‘pleurosphenoids,’ thereby providing useful comparison with morphologically derived recumbirostrans. A cladistic analysis of 60 taxa and 227 characters recovered a monophyletic clade of Huskerpeton, Proxilodon, and the recently described Tambaroter within a more inclusive clade that includes gymnarthrids and ostodolepids (both nested members of the Recumbirostra and putative outgroups to caecilians). Whereas other lepospondyls (i.e., lysorophians) are abundant in the region, the records of Huskerpeton and Proxilodon reveal that only two ‘microsaur’ genera are adequately known from the lowermost Permian of Kansas/Nebraska and demonstrate similarities between the Eskridge and Speiser faunas. Moreover, these forms may represent the ground plan from which more specialized fossorial forms (gymnarthrids and ostodolepids) evolved. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

FIRST FOSSIL ORTHOPTERA FROM THE JURASSIC OF NORTH AMERICA

Abstract A new species of Orthoptera, Parapleurites morrisonensis, is described from the upper Jurassic Morrison Formation of Colorado, USA. This is the first insect described from the Morrison Formation and the first orthopteran described from the Jurassic of North America. No other members of the family Locustopsidae have been described in North America previously, and the other species of Parapleurites are only known from Siberia. The lack of Jurassic Orthoptera in North America is likely due to a combination of taphonomic variables and collector bias. The discovery of Parapleurites morrisonensis and the potential for finding other Jurassic Orthoptera are important to understanding the evolution of this diverse and widely distributed group.