Late Norian Coelophysid Neotheropod (Dinosauria, Saurischia) from Northwestern Argentina

MARTINEZ, RICARDO NESTOR; APALDETTI, CECILIA; GARCIA, GONZALO; SOJO, CAMILA

Los Angeles

Encuentro; Meeting of the Society of Vertebrate Paleontology; 2016

SVP

Coelophysoids are carnivore dinosaurs that lived around Pangaea during the Late Triassic?Early Jurassicand are considered the earliest radiation of neotheropods. Despite its abundant record, the only specieknown for South America is Zupaysaurus rougieri (Mid-Norian of Argentina), a putative coelophysoid ofcontroversial phylogenetic relationship. We present here a new coelophysoid from the Quebrada delBarro Formation (Late Norian), Northwestern Argentina, preserving an articulated vertebral sequencefrom 3rd to 13th presacrals, sacrum composed of five co-ossified vertebrae articulated to the last dorsal andthe first caudal, pelvis lacking distal end of pubis and ischium, and proximal end of left tibia.Phylogenetic analysis placed the new specimen well nested within a monophyletic Coelophysidae in apolytomy with Coelophysis rhodesiensis and Camposaurus arizonensis, and as sister group ofCoelophysis bauri and Lepidus praecisio. Deep pleurocoels on the centrodiapophyseal laminae of theposterior cervical vertebrae differentiates it from other neotheropods. This first record confirms thepresence of coelophysoid neotheropods in South America, providing new information on thecontroversial early evolutionary history of Theropoda during the early Mesozoic of Pangaea.