ESTUDIOS SOBRE LOS ASTRAPOTHERIA (MAMMALIA) DEL PALEOCENO y EOCENO. PARTE II: FILOGENIA, ORIGEN y RELACIONES

Abstract

Main pathways in the evolution of dentition, cranium, mandible and limb bones of the early Astrapotheria are discussed. This it based on the comparison of Eoastrapostylops riolorense Soria and Powell, 1982 with the rest of paleocene-eocene species of Astrapotheria, exposed in Part 1. The family Eoastrapostylopidae Soria and Powell, 1982 is convalidated. An analysis of the affinities between the Astrapotheria and other orders of autochtonous ungulates from the South American Tertiary is given. The author postulates the common origin of the Astrapotheria, Xenungulata, Notoungulata and Pyrotheria, from an ancestral condylarthr stock, different of the Didolontidae, such as was advanced by Soria (1984). This hypothesis involves a fundamental dichotomy in the evolution of these ungulates. Two Superorders are thus recognized: Protungulata, including the Condylarthra and Litoptema, and Meridiungulata, including the Astrapotheria, Xenungulata, Notoungulata and Pyrotheria, and tentatively the Notopterna, proposed by Soria (1984b).