Deep faunistic turnovers preceded the rise of dinosaurs in southwestern Pangaea

MARTINELLI, AGUSTÍN G.; EZPELETA, MIGUEL; TROTTEYN, M. JIMENA; FIORELLI, LUCAS E.; VON BACZKO, M. BELÉN; HECHENLEITNER, E. MARTÍN; EZCURRA, MARTÍN D.; ROCHER, SEBASTIÁN; TABORDA, JEREMÍAS R. A.; DESOJO, JULIA B.

Nature Ecology & Evolution

Nature Publishing Group

Lugar: Londres; Año: 2017 vol. 1 p. 1477 - 1483

The Triassic period documents the origin and diversification of modern amniote lineages and the Late Triassic fossil record ofSouth America has been crucial to shed light on these early evolutionary histories. However, the faunistic changes that led tothe establishment of Late Triassic ecosystems are largely ignored because of the global scarcity of fossils from assemblages afew million years older. Here we contribute to fill this gap with the description of a new tetrapod assemblage from the lowermostlevels of the Chañares Formation (uppermost Middle?lower Late Triassic epochs) of Argentina, which is older than the othervertebrate assemblages of the same basin. The new assemblage is composed of therapsids, rhynchosaurids and archosaurs,and clearly differs from that of the immediately overlying and well-known historical Chañares vertebrate assemblage. The newtetrapod association is part of a phase of relatively rapidly changing vertebrate assemblage compositions, in a time span shorterthan 6 million years, before the diversification of dinosaurs and other common Late Triassic tetrapods in southwestern Pangaea