MUSEO ARGENTINO DE CIENCIAS NATURALES "BERNARDINO RIVADAVIA"
Unidad Ejecutora - UE
The Evolution of the Cenozoic Terrestrial Mammalian Predator Guild in South America: Competition or Replacement?
FRANCISCO J. PREVOSTI; ANALÍA FORASIEPI; NATALIA ZIMICZ
JOURNAL OF MAMMALIAN EVOLUTION
Año: 2011 p. 1 - 1
South America was isolated from other continentsduring most of the Cenozoic, developing a singularmammalian fauna. In contrast to North America, Europe,Asia, and Africa, up to the late Neogene, the carnivoreadaptive zone in South America was populated bycrocodiles (Sebecidae), large snakes (Madtsoiidae), largebirds (Phorusrhacidae), and metatherian mammals (Sparassodonta).Sparassodonta were varied and comprised awide range of body masses (≈ 2?50 kg) and food habits.Their diversity decreased towards the late Miocene (HuayquerianStage/Age) and the group became extinct in the?middle? Pliocene (≈ 3 Ma, Chapadmalalan Stage/Age).Several authors have suggested that the cause of thisdecline and extinction was the ingression of carnivoransto South America (about 6?7 Ma ago), because theycompeted with the Sparassodonta; although this hypothesishas been criticized in recent years. With the intention oftesting the hypothesis of ?competitive displacement,? wereview the fossil record of South American Sparassodontaand Carnivora, collect data about diversity, estimate sizeand diet, and determine first and last appearances. Thediversity of Sparassodonta is low relative to that ofCarnivora throughout the Cenozoic with the early Miocene(Santacrucian Stage/Age) showing the greatest diversitywith 11 species. In the late Miocene-middle Pliocene(Huayquerian Stage/Age), the fossil record shows overlapof groups, and the Sparassodonta?s richness curve begins todecline with the first record of Carnivora. Despite thisoverlap, carnivorans diversity ranged from four or fewerspecies in the late Miocene-Pliocene to a peak of around 20species in the early Pleistocene (Ensenadan Stage/Age).Carnivora was initially represented by small-sized, omnivorousspecies, with large omnivores first appearing in theChapadmalalan Stage/Age. Over this period, Sparassodontawas represented by large and small hypercarnivores and asingle large omnivorous species. From this review of thefossil record, it is suggested that factors other thancompetitive displacement may have caused the extinctionof the Sparassodonta.