On the existence of non-microbiotherian Australidelphian marsupials (Diprotodontia) in the Eocene of Patagonia

LORENTE M; CHORNOGUBSKY L; GOIN FJ

PALAEONTOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2016

0031-0239

From the Patagonian localities of La Barda and Laguna Fría (vicinities Paso del Sapo) in northwestern Chubut Province (Argentina), comes a diverse assemblage of extinct mammals of early-middle Eocene age (Ypresian-Lutetian boundary). Metatherians are well represented, mostly by dental remains of ?Didelphimorphia?, Paucituberculata, Sparassodonta, Microbiotheria, and Polydolopimorphia. Here we analyze three calcanea and one astragalus referable to the same, indeterminate taxon, from La Barda, showing the fusion of their ectal and sustentacular facets. This facet characterizes the Australidelphia, a marsupial clade represented by the South American and Antarctica Microbiotheria plus all Australasian lineages. Other australidelphian features shown by these tarsals include, in the calcanea, a reduced peroneal process and a tripartite cuboid facet; in the astragalus, a round, very small astragalar head in relation to the body; a convex trochlea with a half for the tibia and another, and half in slightly lower position, for the fibula. Their size and other anatomical features suggest that the new tarsals cannot be referred to the Microbiotheria. Phylogenetic analysis suggests that the La Barda taxon lies within the Australidelphia, and that it is either closely related, or belongs to, the Diprotodontia.