Oldest dinosauromorph from South America and the early radiation of dinosaur precursors in Gondwana

Whereas the oldest dinosaur skeletons have been excavated from mid to late Carnian beds of South America, its close relatives occur in Anisian to early Carnian deposits from Argentina, Tanzania and Zambia. These close relative forms are key taxa regarding the investigation of macroevolution of dinosauromorphs. Early dinosaurs are well-documented from Carnian strata of Brazil, whereas the Ladinian deposits lack any unambiguous evidence of dinosauromorphs. Here, we present the first dinosauromorph from the Middle Triassic sediments (Pinheiros-Chiniqua Sequence) of Brazil. The new specimen is a right femur and is from the Dinodontosaurus Assemblage Zone (AZ). This AZ is usually correlated with the Tarjadia AZ from Argentina, which is ascribed to the Ladinian-Carnian boundary and currently lacks any evidence of dinosauromorphs. Therefore, the new specimen is potentially the oldest dinosauromorph from South America, narrowing the biogeographical gap between Africa and Argentina during the early radiation of dinosauromorphs. In addition, the new specimen establishes that dinosauromorphs lived in South America earlier than previously expected, extending the record into the Ladinian.(c) 2022 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

Automated summary

Researchers have discovered the oldest dinosaur morphological fossil in the Middle Triassic sediments of Brazil, narrowing the geographical gap between South America, Africa, and Argentina during the early radiation of dinosaur morphological forms.