Osteología y miología del autopodio posterior en un nuevo dinosaurio Carcharodontosauridae de la Formación Huincul (Cenomaniano-Turoniano, Provincia de Neuquén, Argentina)

Abstract

Bipedalism is the form of locomotion that appeared last in evolution and is in terms of biomechanics one of the most complex for a terrestrial animal. The Carcharodontosauridae are among the most impressively sized theropod dinosaurs and possibly are the bipedal and digitigrade animals that have reached the largest body size. However, the foot osteology and myology of the Carcharodontosauridae theropods are poorly studied topics, due to the fragmentary nature of the known materials and the absence of complete hindlimbs in species derived of the clade (Carcharodontosaurinae). The specimen of Carcharodontosauridae MMCh-PV 65, which is the object of this degree thesis, was found in the lower levels of the Huincul Formation (Cenomanian-Turonian), in the locality of Las Campanas, near Villa El Chocón (Neuquén, Argentina). It is a derived representative of the clade and retains complete and exceptionally preserved posterior autopodium elements, representing an opportunity to study novel osteological elements and integrate inferences on soft tissue, musculature, and ligament reconstruction. The detailed study of the posterior metapodium of this family is, as previously stated, an excellent opportunity to investigate the morphofunctional limits linked to the development of gigantism in bipedal dinosaurs. On the basis of the osteological observations, MMCh-PV 65 has a proportionally shorter and more robust foot than phylogenetically related but smaller taxa, such as Allosaurus, Sinraptor and Concavenator. This tendency to have more robust metatarsals, although not cossified together as in the arctometatarsal condition, has led to the development of powerful musculature and extensive ligamentous insertions. Furthermore, given the completeness of the material, the osteological description will help in defining the characteristics of the Carcharodontosauridae foot, potentially solving future taxonomic doubts linked to the metapodium.