New carcharodontosaurid theropod remains from El Chocón (Neuquén Group, Huincul Formation), Neuquén, Argentina.

JUAN IGNACIO CANALE; SEBASTIÁN APESTEGUÍA; PETER J. MAKOVICKY; PABLO A. GALLINA; GIANECHINI, FEDERICO A.; NATHAN SMITH; IGNACIO MANIEL; ALEJANDRO HALUZA

Buenos Aires

Jornada; XXVI Jornadas Argentinas de Paleontología de Vertebrados; 2012

Universidad Maimónides

The recorded carcharodontosaurid theropods for the Neuquén Group are Giganotosaurus carolinii Coria and Salgado 1995 and Mapusaurus roseae Coria and Currie 2006; from mid-levels of the Candeleros and Huincul formations respectively. Here we present a new theropod from the lower levels of the Huincul Formation, at Las Campanas Creek, near Villa El Chocón, Neuquén. The remains, belonging to a carcharodontosaurid, include several well-preserved cranial and postcranial elements like a near complete left arm (the first for a southern derived carcharodontosaurid). Carcharodontosaurid features of this specimen are a strongly ornamented lateral face of the maxilla, a jugal process of the ectopterygoid at an angle greater than 15º with respect to main body in lateral view, a rectangular distal end of the jugal process of ectopterygoid, and a dorsomedially oriented femoral head. The arm elements are short and robust, with expanded articular ends, as in Acrocanthosaurus. The humerus shows a conspicuous oval depression below the humeral head in the posterodorsal aspect, a trait not recorded yet in any other Allosauroidea. The pubis bears a straight shaft, a synapomorphy shared with all known South American carcharodontosaurids, like Tyrannotitan, Mapusaurus,and Giganotosaurus. The strong and sharp anterolateral flange of the ischium, coupled with pleurocoels in proximal caudal vertebrae, differentiate this form from both Giganotosaurus and Mapusaurus. The new specimen not only increases the general diversity of this peculiar group but also adds information on anatomical aspects that remain obscure.