Muscular correlates on the hindlimb of Skorpiovenator bustingorryi (Abelisauridae, Theropoda)

CERRONI, MAURICIO ANDRÉS; OTERO, ALEJANDRO; CANALE, JUAN IGNACIO; NOVAS, FERNANDO EMILIO

San Luis

Jornada; Reunión de Comunicaciones de la Asociación Paleontológica Argentina; 2017

The hindlimb anatomy of Abelisaurid theropods has been addressed in several contributions, but the osteological correlates associated to the hindlimb muscular arrangement remains obscured. Skorpiovenator bustingorryi Canale, Scanferla, Agnolín and Novas 2008, is an abelisaurid theropod from the Late Cretaceous of North-western Patagonia, Argentina, which provides novel insight on the osteological correlates linked to the hindlimb myology. Under the Extant Phylogenetic Bracket (based on comparisons with crocodiles and birds), the study resulted in the inference of 23 muscles, with a 76% of level I (including I´) and 24% of level II and II´. The bone correlates include reconstruction of several muscles as the m. ambiens, m. iliotibialis, m. femorotibialis, m. ileofemoralis externus, m. iliofibularis, mm. caudofemorales, m. adductor femoris 1, m. gastrocnemii; furthermore, lower legs muscles as well as the extensor and flexor pedal muscles were reconstructed. Interestingly, abelisaurids and tyrannosaurids share anteroposteriorly developed ilia and large tibial cnemial crests possibly related to a greater development of flexor and extensor hindlimb muscles. A well-developed fourth trochanter and a wide brevis fossa would indicate the presence of large mm. caudofemorales in Skorpiovenator , which suggests an arrangement similar to crocodiles rather than birds. Moreover, in Skorpiovenator (and possibly in most abelisaurids) the mm. caudofemorales would have been more developed than in crocodiles, conferring a strong hindlimb retraction and thus probably increasing its cursorial abilities. This preliminary study constitutes the first attempt to reconstruct the hindlimb myology in a South American theropod dinosaur, increasing our knowledge on the hindlimb anatomy of abelisaurids.