GAIA N° 15, LlSBONLISBON, DEZEMBROIDECEMBER 1998, pp.185-192 (I SSN: 0871-5424) ON THE PALAEOBIOLOGY OF THE SOUTH AMERICAN HORNED THEROPOD CARNOTAURUSSASTREI BONAPARTE Gerardo V. MAZZETTA Departamento de Paleontologia, Facultad de Ciencias, [gua 4225,11400 MONTEVIDEO. URUGUAY E-mail: mazzetta@fcien.edu.uy Richard A. FARINA Departamento de Paleontologia, Facultad de Ciencias, [gua 4225,11400 MONTEVIDEO. URUGUAY E-mail:farina@fcien.edu.uy Sergio F. VIZCAiNO Departamento CientificQ Paleontologia Vertebrados, Facultad de Giencias Naturales y Museo, Universidad Nacional de La Plata, Paseo del Bosque sin, 1900 LA PLATA. ARGENTINA E-mail: vizcaino@netverk.com.ar ABSTRACT: Some palaeobiological traits of the horned carnivorous dinosaur Carnotaurus BONAPARTE are assessed. Its body mass and indicator of athletic capabilities are estimated. A model ofthe jaw mechanics is proposed, including the analysis ofthe cranial kinesis. Fur- ther, the strength of the horns, head and neck muscles are studied. It is concluded that Car- notaurus was an agile theropod, with a somewhat fast rather than strong bite, and that it must have used the horns in intraspecific fights or even in hunting. RESUMO: Neste trabalho, discutem-se alguns aspectos paleobiologicos do dinossaurio car- nivoro com cornos Carnotaurus BONAPARTE. Sua massa corporal e a sua capacidade ca foram estimados . Propoe-se urn modelo da mecanica mandibular, incluindo uma analise da cinetica do cranio. Alem disto, a resistencia dos cornos, cabe!ia e pesc0!i0 e estudada. Conclui-se que Carnotaurus era urn teropode agil, com uma mordida mais rapida do que for- te e que deve ter usado seus cornos para lutas intraespecificas ou mesmo para a ca!ia. INTRODUCTION Carnotaurus sastrei BONAPARTE, 1985, is a very interesting and unusual theropod from the Creta- ceous of South America. In spite of the fact that some theropods are known to have bony structures on the skull (like longitudinal crests as in Dilopho- saurus WELLES and Syntarsus RAATH or a single na- sal horn as in Ceratosaurus MARSH and Procera- tosaurus HUENE), this is the only example described of a horned carnivore with a pair of stout frontal horns, either among dinosaurs or mammals. Carnotaurus is based on an exceptionally well preserved and almost complete skeleton with all of the bones perfectly articulated, and at present is the best known theropod from the Gondwanian conti- nents (BONAPARTE, 1996). This remarkable speci- men was collected in the lower section of La Colonia Formation (ARDOLINO & DELPINO, 1987), Lower- Upper Cretaceous, Chubut Province, Argentina. Al- though the skull shows very different proportions from those of Abelisaurus comahuensis BONAPARTE & NOVAS, 1985, it bears diagnostic characters of the Abelisauridae such as the large infratemporal fen- estra, the elongated quadrate, the quadratojugal fused with the quadrate, the contact of lachrimal and postorbital above the orbit, the reduced preantorbi- tal fenestra, the posteriorly directed squamosal with a ventral, rod-like process, and the narrow dorsal process of the maxilla (NOVAS, 1989). Following BONAPARTE, NOVAS & CORIA (1990), these shared cranial features suggest that both Carnotaurus and Abelisaurus belong to the same family, Abelisauri- dae, as defined by BONAPARTE & NOVAS (1985). The 185 artigos/papers