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Abstract The rapid radiation and dispersal of crown reptiles following the end‐Permian mass extinction characterizes the earliest phase of the Mesozoic. Phylogenetically, this early radiation is difficult to interpret, with polytomies near the crown node, long ghost lineages, and enigmatic origins for crown group clades. Better understanding of poorly known taxa from this time can aid in our understanding of this radiation and Permo‐Triassic ecology. Here, we describe an Early Triassic specimen of the diapsidPalacrodonfrom the Fremouw Formation of Antarctica. WhilePalacrodonis known throughout the Triassic and exhibits a cosmopolitan geographic range, little is known of its evolutionary relationships. We recoverPalacrodonoutside of crown reptiles (Sauria) but more crownward thanYoungina capensisand other late Permian diapsids. Furthermore,Palacrodonpossesses anatomical features that add clarity to the evolution of the stapes within the reptilian lineage, as well as incipient adaptations for arboreality and herbivory during the earliest phases of the Permo–Triassic recovery.
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The postcranial anatomy of Moschorhinus kitchingi (Therapsida: Therocephalia) from the Karoo Basin of South Africa
Therocephalia are an important clade of non-mammalian therapsids that evolved a diverse array of morphotypes and body sizes throughout their evolutionary history. The postcranial anatomy of therocephalians has largely been overlooked, but remains important towards understanding aspects of their palaeobiology and phylogenetic relationships. Here, we provide the first postcranial description of the large akidnognathid eutherocephalianMoschorhinus kitchingiby examining multiple specimens from fossil collections in South Africa. We also compare the postcranial anatomy with previously described therocephalian postcranial material and provide an updated literature review to ensure a reliable foundation of comparison for future descriptive work.Moschorhinusshares all the postcranial features of eutherocephalians that differentiate them from early-diverging therocephalians, but is differentiated from other eutherocephalian taxa by aspects concerning the scapula, interclavicle, sternum, manus, and femur. The novel anatomical data from this contribution shows thatMoschorhinuspossessed a stocky bauplan with a particularly robust scapula, humerus, and femur. These attributes, coupled with the short and robust skull bearing enlarged conical canines imply thatMoschorhinuswas well equipped to grapple with and subdue prey items. Additionally, the combination of these attributes differ from those of similarly sized coeval gorgonopsians, which would have occupied a similar niche in late Permian ecosystems. Moreover,Moschorhinuswas the only large carnivore known to have survived the Permo-Triassic mass extinction. Thus, the subtle but important postcranial differences may suggest a type of niche partitioning in the predator guild during the Permo-Triassic mass extinction interval.
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- Award ID(s):
- 2325381
- PAR ID:
- 10569967
- Publisher / Repository:
- PeerJ
- Date Published:
- Journal Name:
- PeerJ
- Volume:
- 12
- ISSN:
- 2167-8359
- Page Range / eLocation ID:
- e17765
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.7717/peerj.17765
