Functional-adaptive analysis of the postcranial skeleton of a Laventan borhyaenoid, Lycopsis longirostris (Marsupialia, Mammalia)

Abstract

ABSTRACT Lycopsis longirostris, a middle Miocene Colombian borhyaenoid, is compared functionally with early Miocene borhyaenoids from Patagonia and the Tasmanian thylacine Thylacinus cynocephalus, the largest Recent marsupial carnivore. The postcranium of Lycopsis shows a mosaic of features. Although several features characterizing the long bones are consistent with a primarily terrestrial mode of life (e.g., a straight ulna and tibia, a semi-digitigrade forefoot), other features like the development of mm. spinati, pectoralis and biceps and the pseudo-opposable pollex indicate that the forelimb had manipulative and grasping abilities. On the hindlimb, the poorly stabilized lower ankle joint, the short metatarsals, and the well-developed hallux also preclude fast running. When compared to three early Miocene borhyaenoids, Prothylacinus patagonicus, Cladosictis patagonica, and Borhyaena tuberata, which form a morphological gradient from the most arboreally-adapted taxon to an incipient cursorial one, Lycopsis is placed between Cladosictis and Borhyaena. Lycopsis was more likely an ambush hunter than a pounce-pursuit predator, stalking small-to medium-sized prey.