First occurrences of Poposauroidea (Archosauria: Paracrocodylomorpha) from North Carolina expand their geographic range in the Late Triassic

Poposauroids (Pseudosuchia; Paracrocodylomorpha) are one of several lineages of ecologically unique archosauriform reptiles that diversified throughout the Triassic Period. Fossils of the poposauroid lineages Shuvosauridae and Poposaurus are well known from Late Triassic deposits across western Pangaea, represented by abundant materials in the southwestern United States in the Chinle Formation and the Dockum Group and rarer occurrences in the Ischigualasto Formation of Argentina. However, Late Triassic records of these lineages are currently unknown in other parts of Pangaea. Here, we extend the geographic range of Late Triassic poposauroids by reporting two incomplete femora from the Newark Supergroup of the eastern United States. Both specimens are from the Chatham Group of North Carolina, the first (NCSM 27054) from a quarry near Wadesboro in Anson County (Cumnock Formation), and the second (AMNH FR 24431) from a quarry near Gulf in Chatham County (Pekin Formation). Both possess diagnostic character states of Poposauroidea and the more complete specimen, NCSM 27054, lacks character states of shuvosaurids. We conclude that these femora represent poposauroids similar (if not identical) to Poposaurus gracilis among known taxa in the clade. Our findings expand the Late Triassic range of Poposauroidea into the central/eastern Pangaean Atlantic rift zone. NCSM 27054 and AMNH FR 24431 may represent some of the oldest Late Triassic poposauroid fossils and help fill a gap in the stratigraphic range of Poposauroidea.