Re‐description of the early Triassic diapsid Palacrodon from the lower Fremouw formation of Antarctica

• Published in: Journal of anatomy Vol. 241; no. 6; pp. 1441 - 1458
• Main Authors: Jenkins, Kelsey M., Meyer, Dalton L., Lewis, Patrick J., Choiniere, Jonah N., Bhullar, Bhart‐Anjan S.
• Format: Journal Article
• Language: English
• Published: Oxford Wiley Subscription Services, Inc 01.12.2022
• Subjects: Adaptation; arboreal; evolution; fossil; Fossils; Herbivory; mass extinction; Mass extinctions; Mesozoic; paleontology; Permian; Phylogeny; Radiation; reptile; stapes; Triassic; Antarctica
• ISSN: 0021-8782; 1469-7580
• DOI: 10.1111/joa.13770

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 diapsid Palacrodon from the Fremouw Formation of Antarctica. While Palacrodon is known throughout the Triassic and exhibits a cosmopolitan geographic range, little is known of its evolutionary relationships. We recover Palacrodon outside of crown reptiles (Sauria) but more crownward than Youngina capensis and other late Permian diapsids. Furthermore, Palacrodon possesses 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. “In the wake of the end‐Permian mass extinction, we show that Palacrodon possesses incipient adaptions for semi‐arboreality and a transitional phase of hearing abilities.”