Paleoecology of the mammalian carnivores (Metatheria, Sparassodonta) of the Santa Cruz Formation (late Early Miocene)

PREVOSTI, F.J.; FORASIEPI, A.M.; ERCOLI, M.; TURAZZINI, G.

Buenos Aires

Jornada; XXVI Jornadas Argentinas de Paleontología de Vertebrados; 2012

During most of the Cenozoic, the predator guild in South America was mainly occupied by metatherians (Sparassodonta) and shared with other vertebrates (Phorusrhacidae Sebecidae, and Madtsoiidae). The Sparassodonta was a diverse clade, recorded from the Paleocene?middle Pliocene, with its acme in the late Early Miocene (Santacrucian Age). We reviewed the paleoecology of the Santacrucian sparassodonts and included new results obtained by geometric morphometric analyses. The Santa Cruz Formation contains eleven sparassodont species: Acyon tricuspidatus Mercerat, Cladosictis patagonica Ameghino, Sipalocyon gracilis Ameghino, S. obusta Ameghino, Pseudonotictis pusillus Ameghino, Perathereutes pungens Ameghino, Prothylacynus patagonicus Ameghino, Lycopsis torresi Cabrera, Borhyaena tuberata Ameghino, Acrocyon sectorius Ameghino, and Arctodictis munizi Mercerat. These sparassodonts were primarily hypercarnivores (according to the tooth morphology), had different locomotor abilities (from scansorial to terrestrial), and a wide range of body mass (between 1 kg and more than 50 kg). The reconstruction of the Santacrucian predator guild suggests that there was a good ecological separation within sparassodonts, given by the combination of the three parameters: body-size, diet, and locomotion. Even without taken into account the already recognized bias of the fossil record, the diversity of sparassodonts in the Santa Cruz Formation (eleven species) and in the lower Estancia La Costa Member of the Santa Cruz Formation (seven species), is similar to that recorded in some past and present placental hypercarnivore communities (e.g., nowadays Patagonian Steppe or the Pampean Region have 12 species of terrestrial carnivores and less than eight hypercarnivores).