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Abstract Eopneumatosuchus colbertiCrompton and Smith, 1980, known from a single partial skull, is an enigmatic crocodylomorph from the Lower Jurassic Kayenta Formation. In spite of its unique morphology, an exceptionally pneumatic braincase, and presence during a critical time period of crocodylomorph evolution, relatively little is known about this taxon. Here, we redescribe the external cranial morphology ofE.colberti, present novel information on its endocranial anatomy, evaluate its phylogenetic position among early crocodylomorphs, and seek to better characterize its ecology. Our examination clarifies key aspects of cranial suture paths and braincase anatomy. Comparisons with related taxa (e.g.,Protosuchus haughtoni) demonstrate that extreme pneumaticity of the braincase may be more widespread in protosuchids than previously appreciated. Computed tomography scans reveal an endocranial morphology that resembles that of other early crocodylomorphs, in particular the noncrocodyliform crocodylomorphAlmadasuchus figarii. There are, however, key differences in olfactory bulb and cerebral hemisphere morphology, which demonstrate the endocranium of crocodylomorphs is not as conserved as previously hypothesized. Our phylogenetic analysis recoversE.colbertias a close relative ofProtosuchus richardsoniandEdentosuchus tienshanensis, contrasting with previous hypotheses of a sister group relationship with Thalattosuchia. Previous work suggested the inner ear has some similarities to semi‐aquatic crocodyliforms, but the phylogenetic placement ofE.colbertiamong protosuchids with a terrestrial postcranial skeletal morphology complicates paleoecological interpretation.
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New insights into the cranial osteology of the Early Cretaceous paracryptodiran turtle Lakotemys australodakotensis
Lakotemys australodakotensis is an Early Cretaceous paracryptodire known from two shells and a skull from the Lakota Formation of South Dakota, USA. Along with the Early Cretaceous Arundelemys dardeni and the poorly known Trinitichelys hiatti , Lakotemys australodakotensis is generally retrieved as an early branching baenid, but more insights into the cranial anatomy of these taxa is needed to obtain a better understanding of paracryptodiran diversity and evolution. Here, we describe the skull of Lakotemys australodakotensis using micro-computed tomography to provide the anatomical basis for future phylogenetic analyses that will be needed to investigate more precisely the intrarelationships of Paracryptodira . Preliminary comparisons reveal that the cranial anatomy of Lakotemys australodakotensis is very similar to that of the Aptian-Albian basal baenid Arundelemys dardeni , that both taxa exhibit a remarkable combination of derived characters found in baenodds and characters found in non-baenid paracryptodires, particularly Pleurosternidae , and that Lakotemys australodakotensis is the only known baenid to date to possess a canal for the palatine artery.
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- Award ID(s):
- 1925896
- PAR ID:
- 10349202
- Date Published:
- Journal Name:
- PeerJ
- Volume:
- 10
- ISSN:
- 2167-8359
- Page Range / eLocation ID:
- e13230
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.7717/peerj.13230
