A NEW GIANT TITANOSAUR FROM THE EARLY CRETACEOUS OF CHUBUT SHEDS LIGHT TO GIANT TITANOSAUR EVOLUTION

JOSÉ LUIS CARBALLIDO; DIEGO POL; ALEJANDRO OTERO; IGNACIO A. CERDA; LEONARDO SALGADO; ALBERTO GARRIDO; JUAN RAMEZZANI; RUBÉN CÚNEO; MARCELO KRAUSE

Jornada; XXIX Jorndas Argentinas de Paleontología de Vertebrados; 2016

Sauropod dinosaurs were the dominant mega-herbivore vertebrates through all the Mesozoic era. Although almost all sauropods can be recognized as giants, some patagonian titanosaur sauropods reached the maximum sizes registered forland vertebrates. Therefore they are of great importance for understanding body size evolution among sauropods. Despite that, the phylogenetic relationships of these titanosaurs are poorly known, as well as their precise body mass. Here wepresent a new extremely giant titanosaur from the late Early Cretaceous of the Chubut Group (Cerro Barcino Formation; Albian). The new titanosaur is represented by, at least, 6 specimens with different degrees of preservation, and being two of them more complete than the others (MPEF-PV 3400 and 3399). Different unique characters are supporting the identification of a new taxon (vertical prezygodiapophyseal lamina in anteriormost dorsals; hyposphene-hypantrum restricted to D3-D4; extremely wide and incipiently bifid anterior caudal neural spines; femur with straight laterodistal edge). The new taxon is represented by a single tooth, cervical, dorsal, and caudal vertebrae, as well as most of the bones that compose the fore- and hind-limbs (with the exception of the hand and pes). The anatomical information reveals an extremely elongatedneck, a comparatively short trunk, and a long robust tail. The amount of anatomical information recovered for the new taxon allows us to make detailed comparisons with other titanosaurs, including giant taxa such as Dreadnoughtus, Argentinosaurus or Futalognkosaurus. The phylogenetic analysis recovered it as a relatively basal titanosaur, which body mass can be adequately estimated based on different approaches.