A new baenid, "Trinitichelys" maini sp. nov., and other fossil turtles from the Upper Cretaceous Arlington Archosaur Site (Woodbine Formation, Cenomanian), Texas, USA (original) (raw)
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Journal of Paleontology, 2016
New cranial and postcranial material of the baenid turtle Neurankylus from the Paleocene Nacimiento Formation (Torrejonian NALMA) of northwestern New Mexico represents a new species, Neurankylus torrejonensis. The material consists of a fragmented but mostly complete skull, a partial carapace and plastron, portions of both humeri, a partial pelvis, a complete right femur, and a distal phalanx. The small, undivided cervical scale, wide vertebrals, complete ring of marginals, and large size (carapace length 520 mm) diagnose the new taxon as belonging to Neurankylus. The narrow fifth vertebral scale and scalloped posterior shell margin reveal affinities with Neurankylus baueri Gilmore, 1916, which is known from Campanian sediments in New Mexico and Utah. The holotype of Neurankylus torrejonensis is the youngest known specimen of the Neurankylus lineage, which is known to reach at least back to the Late Cretaceous (Santonian). A nearly complete species-level analysis of baenids confirms the basal placement of Neurankylus outside of Baenodda and the split of Baenodda into two primary subclades, herein named Palatobaeninae and Eubaeninae. Remarks.-For a recent review of taxa classified within Neurankylus, please refer to Larson et al. (2013) and Joyce and Lyson (2015). Neurankylus torrejonensis new species
The Mesaverde Formation of the Wind River and Bighorn basins of Wyoming preserves a rich yet relatively unstudied terrestrial and marine faunal assemblage dating to the Campanian. To date, turtles within the formation have been represented primarily by isolated fragments diagnostic only to broader clades. A baenid specimen from the lower third of the Mesaverde Formation in the northwestern Bighorn Basin of Park County, Wyoming, includes a partial carapace and plastron and is the most complete turtle specimen yet described from the formation. The entire carapace would have been around 450 mm long and 380 mm wide, indicating a fairly large individual. The preserved portions of the carapace are smooth and unornamented, and the overall oval dorsal profile of the shell is similar to taxa such as Neurankylus spp. The anterior plastral lobe in the new specimen is squared off in profile as seen in Neurankylus spp., unlike the more rounded or triangular condition in Boremys spp., Eubaena hat...
Morphology and Evolution of Turtles
The fossil turtles from the Upper Cretaceous Fruitland and Kirtland formations (late Campanian; Kirtlandian) have been known for more than 100 years. We re-assess and revise these Late Cretaceous testudine taxa from the San Juan Basin, New Mexico, USA, and discuss their biostratigraphic distribution. We recognize the following valid taxa as present: the bothremydid Chedighaii hutchisoni; the pleurosternid Compsemys sp.; the baenodds Denazinemys nodosa and Scabremys gen. nov., established for the distinct species S. ornata, previously included in Denazinemys; and Boremys grandis, though it is a rare taxon. The non-baenodd baenid Neurankylus baueri is recognized as a valid species. Two additional non-baenodd baenid taxa, Thescelus hemispherica and T. rapiens, are retained as distinct species and are not considered synonymous with T. insiliens. We also recognize a small indeterminate kinosternoid similar to that reported from the Campanian of Mexico. The two adocids Adocus bossi and A. kirtlandius are retained as distinct species. The nanhsiungchelyid Basilemys gaffneyi sp. nov. is established, whereas Basilemys nobilis is considered a nomen dubium because it lacks the diagnostic features that would allow referral to any known valid species. We recognize three trionychids: Aspideretoides austerus and A. robustus (new combination), and an unnamed plastominine. We synomize Aspideretoides fontanus and A. vorax with A. austerus. Aspideretoides ovatus is considered a subadult of A. robustus. The unnamed plastominine may represent a new genus and species. Turtles of the Fruitland-Kirtland formations resemble other late Campanian turtle assemblages from western NorthAmerica, and are part of the characteristic vertebrate fauna of the Kirtlandian land-vertebrate age. The upper Fruitland and lower Kirtland formations (Hunter Wash local fauna) have greater turtle taxonomic diversity than the upper Kirtland Formation (Willow Wash local fauna). This apparent decrease in taxonomic diversity is interpreted as being real and reflects a shift in depositional (channel) environments to a more terrestrial one, a pattern which is seen in other North American Late Cretaceous settings.