A new sauropodiform (Dinosauria, Sauropodomorpha) from the Late Triassic Quebrada del Barro Formation (Marayes-El Carrizal Basin), San Juan Province, Argentina.

APALDETTI, CECILIA; MARTINEZ, RICARDO NESTOR; ABELÍN, DIEGO

Buenos Aires

Jornada; XXX Jornadas Argentinas de Paleonotología de Vertebrados.; 2016

MACN

The Late Norian Quebrada del Barro Formation (QBF) of the continental Marayes?El Carrizal Basin (Northwestern Argentina) had recently provided a new vertebrate assemblage. Among those vertebrate groups, sauropodomorph dinosaurs are one of the most abundant and diverse, including basal and derived forms. Here we present a new sauropodomorph (PVSJ 908), which exhibits some anatomical features that resemble the basal Sauropoda condition. PVSJ 908 consists in a partial postcranial skeleton including anterior-mid cervical and articulated anterior-mid dorsal vertebrae, proximal humerus, radius, ulna, partial manus, femur, distal tibia, astragalus, and almost complete articulated pes. The presence of strongly high dorsal neural arches (twice the centrum height), a reduced expansion of the proximal humerus with straight and not well-developed deltopectoral crest, and rounded fourth trochanter at mid-length of the femur, among others, difference the PVSJ 908 from basal sauropodomorphs (i.e., Riojasaurus and Coloradisaurus) from the Norian Los Colorados Formation (LCF). PVSJ 908 has a triangular astragalus with a rounded posteromedial corner and more reduced manus and pes than Lessemsaurus, the most derived sauropodomorph from LCF. Preliminary phylogenetic analysis depicts PVSJ 908 within Sauripodiformes in a politomy with Leonerasaurus, Aardonyx, and Sefapanosaurus, and more derived than the Jurassic Mussaurus. Further studies of this new taxon and other sauropodomorphs recently discovered at the QBF offer new understanding about the evolution of basal Sauropodomorpha and the origin of Sauropoda; and together with the rest of the QBF fauna shed light about the evolution of terrestrial vertebrate ecosystems during the early Mesozoic of Southern Pangea.