INVESTIGADORES
SOIBELZON Leopoldo Hector
congresos y reuniones científicas
Título:
Sparassodonta vs. Carnivora: ecological relationships between carnivorous mammals in South America
Autor/es:
PREVOSTI, F.; FORASIEPI, A.; LEOPOLDO HECTOR SOIBELZON; ZIMICZ, N.
Lugar:
Mendoza
Reunión:
Congreso; 10th. International Mammalogical Congress.; 2009
Resumen:
South America was isolated from other continents
during most of the Tertiary, developing a very particular mammalian fauna. In
contrast to other continents, the carnivore adaptative zone was filled by
crocodiles (Sebecidae), large snakes (Madtsoiidae), large birds
(Phorusrhacidae), and metatherian mammals (Sparassodonta). Sparassodonta was
diverse during the Tertiary and comprised a broad range of sizes (≈ 2-50 kg). This diversity decreased
towards the late Miocene (Huayquerian) and the group became extinct at the
middle Pliocene (≈ 3 Ma, Chapadmalalan). Several authors have suggested that
the cause of this decline and extinction was the ingression of placental
Carnivores to South America (about 6-7 Ma
ago), because they putatively competed with the Sparassodonta. This hypothesis
was criticized in recent years. With the intention of testing the hypothesis of
competitive displacement, we review the fossil record of South American Sparassodonta
and Carnivora, collect data about diversity, first and last appearances, and
estimate size and diet of the involved taxa. The diversity of Sparassodonta is
low relative to that of Carnivora all along the Tertiary. The highest number is
found in the early Miocene (Santacrucian), with more than 10 species. The
fossil record shows overlap of groups during the late Miocene-middle Pliocene, and
the Sparassodontas richness curve declines since the first record of the
Carnivora during the Huayquerian. Despite this overlap, carnivores were
represented by 4 or less species during the late Miocene-Pliocene, and their
diversity reached values of about 20 species only in the early Pleistocene
(Ensenadan). Moreover, Carnivora was first represented by small-sized, omnivore
species, with large omnivores first appearing in the Chapadmalalan. During this
period, Sparassodonta was represented by large and small hypercarnivores and a single
large mesocarnivore species. These data suggest that factors other than
competitive displacement may have caused the extinction of the Sparassodonta.