Marsupiais do inicio do terciário do Brasil: origem, irradiação e história biogeografica

OLIVEIRA EV; GOIN FJ

Os Marsupiais do Brasil: Biologia, Ecologia e Evoluçao

Editora UFMS

Lugar: Campo Grande; Año: 2006; p. 299 - 320

The phylogenetic and biogeographic significance of the marsupial fauna of Itaboraí (middle Paleocene, Brazil) is discussed. All major lineages (orders) of South American Cenozoic marsupials are already present in the Itaboraí fauna: Peradectia, Sparassodonta, Didelphimorphia, Paucituberculata, Polydolopimorphia, and Microbiotheria. Peradectians are represented by a few peradectine, caroloameghiniid, and pediomyid opossums. Sparassodonts include small, generalized forms as Patene, whose overall dental morphology, together with that of earlier (Tiupampian) borhyaenoids, suggest that their origin is not from didelphimorphians but from peradectine or peradectine-like peradectians. The large variety of Itaboraian didelphimorphians include herpetotheriines, derorhynchines, and the specialized protodidelphids; together, they seem to belong to an early clade of didelphimorphians probably representing the sister-group of modern (Neogene) didelphid opossums. Derorhynchines have several derived dental features suggesting affinities with peramelemorphians. The oldest known Paucituberculata is also recorded in Itaboraí; its dental morphology suggests that the plagiaulacoid-like molar of palaeothentids and abderitids may constitute the persistence in these lineages of the deciduous premolar. Polydolopimorphians were supposed to be exclusively represented in Itaboraí by epidolopines; however, arguments that glasbiid opossums (also present in Itaboraí) may constitute early, plesiomorphic polydolopimorphians, are discussed. Glasbiids and microbiotheriids may, in turn, represent sister taxa, thus suggesting affinities between polydolopimorphians (in this broader concept) with the Australian diprotodonts. A biogeographic model on the origin and radiation of South American marsupials is presented. Even though North American in origin, South American taxa, especially the Paleocene ones, seem to be key for the interpretation of the African, Eurasian, Antarctic, and Australian radiation of marsupials.