The Early Radiation of Sauropodomorphs in the Carnian (Late Triassic) of South America

LANGER, M.C.; BRONZATI, M.; MARSOLA, JÚLIO CÉSAR DE ALMEIDA; TEMP MÜLLER, RODRIGO; BITTENCOURT, J. S.; APDALDETTI, C.; EZCURRA, M.D.

Springer Earth System Sciences

Springer Nature Switzerland

Año: 2022

2197-9596

Carnian (Late Triassic) deposits of South America provide the oldest2 unequivocal dinosaur records worldwide, most of which has been assigned3 to the sauropodomorph lineage. This includes Eoraptor lunensis, Panphagia4 protos, and Chromogisaurus novasi, from the Ischigualasto Formation, Argentina,5 and Saturnalia tupiniquim, Pampadromaeus barberenai, Buriolestes schultzi, and6 Bagualosaurus agudoensis, from the Santa Maria Formation, Brazil. Here, we demonstrate that their holotypes anatomically differ from one another, supporting8 the taxonomic validity of the species. In addition, a morphological disparity anal9ysis, with significant statistical support, clustered some of the better-known spec10imens of E. lunensis, Sat. tupiniquim, and Bu. schultzi, with the respective holo11types. For the latter two taxa, this was corroborated by a specimen-level phyloge12netic analysis that also found Ba. agudoensis as the sister taxon to post-Carnian13 sauropodomorphs. Our results also suggest that Bu. schultzi and E. lunensis are the14 earliest branching sauropodomorphs and that Sa. tupiniquim and Pam. barberenai15 are closer to Bagualosauria. A species-level phylogenetic analysis further suggests16 that Bu. schultzi and E. lunensis form a clade that Sa. tupiniquim is the sister taxon17 to Bagualosauria and that Pan. protos and Ch. novasi are also more highly nested,18 forming a clade with Pam. barberenai.