A Late Norian—Rhaetian Coelophysid Neotheropod (Dinosauria, Saurischia) from the Quebrada Del Barro Formation, Northwestern Argentina

APALDETTI, CECILIA; MARTÍNEZ, RICARDO N.

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Año: 2017 vol. 54 p. 488 - 505

0002-7014

Coelophysoids are the most abundant theropod dinosaurs known from Late Triassic through Early Jurassic which represent the earliest major radiation of Neotheropoda. Within Coelophysoidea sensu lato the most stable clade is the family Coelophysidae, small theropods characterized by its long neck and light and kinetic skull. Coelophysids are the most abundant basal non-Tetanurae neotheropods known worldwide, but until recently they were unknown from South America. We report here a new coelophysid neotheropod, Lucianosaurus bonoi gen. et sp. nov., from the Late Norian-Raethian Quebrada del Barro Formation, Northwestern Argentina. A phylogenetic analysis recovers Lucianosaurus bonoi nested into the monophyletic group Coelophysidae in an unresolved clade together with Coelophysis rhodesiensis and Camposaurus arizonensis. The presence of Lucianosaurus in the Late Norian-Raethian of Argentina increases the poor and scarce record of Triassic South American neotheropods, suggesting that the virtual absence of theropods in the fossil record during the Raethian is probably a taphonomic/stratigraphic bias instead a decline of diversity and abundance after the Norian. Finally, the new find corroborates the American endemism in the Late Triassic and worldwide distribution during the Early Jurassic of coelophysid neotheropods, supporting the extreme faunal homogeneity hypothesized for Early Jurassic continental biotas.