Hindlimb musculature of Neuquensaurus australis Lydekker (Sauropoda, Titanosauria)

ALEJANDRO OTERO ; SERGIO F. VIZCAÍNO

Córdoba

Congreso; IX Congreso Argentino de Paleontología y Bioestratigrafía; 2006

Academia Nacional de Ciencias

Saltasaurinae (Late Cretaceous of South America) includes the most derived titanosaur sauropods. They are characterized by their small size and by some features at their appendicular skeleton, such as a well developed femoral lateral bulge, preacetabular lobe of the ilium nearly horizontal and laterally projected, and a well developed fibular lateral trochanter (Salgado et al., 1997; Wilson and Sereno, 1998) suggesting particular locomotor habits. Few contributions describe these particularities, and no attention has been paid to the reconstruction of the appendicular musculature. The relationship between locomotor habits and shape of the appendicular skeleton and its associated musculature is well documented in living crocodiles and lizards (Blob and Biewener, 2001), as well as in living mammals (Biewener, 1989). The goal of this contribution was to reconstruct the musculature and to study some morphofunctional aspects of the hindlimb of the saltasaurinae sauropod Neuquensaurus australis Lyddeker (Museo de La Plata, MLP CS 1002; 1021; 1056; 1093; 1107; 1258; 1265; 1294; Ly 127; and Museo de Cinco Saltos, MCS 5; MCS 6; MCS 9). To do this, we considered that muscles that have the same rough positions and connections in extant archosaurs (crocodiles and birds) can reasonably be inferred to have had the same features in dinosaurs, and thus be placed in a musculoskeletal model with confidence (Extant Phylogenetic Bracket, Witmer, 1995, 1997). We reconstructed principal muscles groups of the leg as Triceps femoris, Iliofibularis, Adductores femores, Ischiotrochantericus and Caudofemorales. We did not reconstruct muscles whose homologies are controversial (e. g. Deep dorsal group). The probable function of each muscle was evaluated by comparison with living analogs, principally mammals, because they provide a better model for understanding muscles function in non-avian dinosaurs (Carrano, 1998; 1999; 2001). This analysis suggests that Neuquensaurus had well developed muscles iliotibialis in relation to the well developed preacetabular ilium, femorotibialis in relation to the mediolateral development of the femur, and iliofibularis due to the large fibular lateral trochanter.