The Cenozoic terrestrial mammalian predator guild in South America: the results of the most recent land connection between the Americas

A.M. FORASIEPI; PREVOSTI, F.J.; ZIMICZ, N.

General Roca

Simposio; Istmos y rutas marítimas: las conexiones biogeográficas en el Hemisferio Sur a través del tiempo; 2011

Universidad Nacional de Río Negro

During most of the Cenozoic, the carnivore adaptative zone in South America was filled by crocodiles (Sebecidae), snakes (Madtsoiidae), birds (Phorusrhacidae), and metatherian mammals (Sparassodonta). Since the Huayquerian, eutherian mammals (Carnivora) started to occupy the niche, becoming today the principal component. Several authors have suggested that the ingression of the Carnivora caused the decline and extinction of the Sparassodonta, because they putatively competed. With the intention of testing this hypothesis, we collect data about diversity, first and last appearances, and estimate size and diet. Sparassodonta is known by 58 species, registered from the Tiupampan to the Chapadmalalan. The taxa had different sizes and mostly a hypercarnivorous diet. The diversity is low (five taxa or less) during most ages; the highest number is found in the Santacrucian (eleven species). In South America, Carnivora is known by 82 terrestrial taxa, of which 37 are extinct and 45 are living species. They were represented by four or less species from the Huayquerian to Marplatan, reaching values of about 20 species only in the Ensenadan. Carnivora was first represented by small, omnivore species, with large omnivores first appearing in the Chapadmalalan. There was overlap of carnivorous groups during the Huayquerian-Chapadmalalan, but there does not appear to have been ecological one. This does not support the competitive displacement hypothesis and is more in line with an opportunistic ecological replacement. The decline and extinction of the Sparassodanta appear to be part of a larger faunistic change in which intrinsic (biological) and external (physical) factors are combined.