Análise funcional do esqueleto apendicular de um marsupial australiano do Mioceno

Abstract

Studies on the functionality of the postcranial skeleton of mammals provide insights on the ecology of extinct mammals. In this context, the fossil of the thylacine Nimbacinus dicksoni (Marsupialia, Thylacinidae) is one of the most completed fossil from the carnivorous marsupial fauna of the Australian Miocene. The appendicular postcranial skeleton of this fossil specimen was analysed and functionally compared to a borhyaenoid from the South American Miocene, Lycopsis longirostris. The latter was selected for comparison because they were contemporary and had similar body sizes. N. dicksoni has a combination of features suggestive of arboreality. Forelimb characteristics are as follows: (1) the deltopectoral crest and the lateral epicondyle of the humerus are well developed; (2) the distal epiphysis of the humerus is asymmetrical; (3) the olecranon of the ulna is short; and (4) the diaphysis of the radius is curved. These suggest that N. dicksoni was able of using its forelimbs for manipulation and climbing. Moreover, on the hindlimbs indicate an efficient performance of abductive movies of the feet. The following hind limbs features reinforce this hypothesis: (1) the laterally oriented acetabulum; (2) the asymmetry of the distal epiphysis of the femur and of the tibial condyles; (3) the robust fibula; (4) the transversally wider astragalonavicular facet and the concave calcaneoucuboid facet. In conclusion, N. dicksoni was mainly a scansorial marsupial, with great hability of manipulating food.