New association of Paleogene Mammals in Eastern of Patagonia (Chubut Province, Argentina): biochronological and paleobiogeographical implications.

Abstract

The continental fossil mammals found in Barrancas Blancas, (near Camarones, Southeast of Chubut Province, Argentina) constitute a new faunal association from the Paleogene of Patagonia. From the base to the top, the outcrop in this locality is composed of continental and marine sedimentites, assigned to Sarmiento Formation and Chenque Formation, respectively. The fossil mammals that represent the new association (mainly Xenarthra, Notoungulata and Litopterna) come from the lower section of the Sarmiento Formation. The following taxa have been recognized: Xenarthra, Cingulata, Dasypodidae, Euphractinae, Eutatini: Meteutatus percarinatus; Euphractini: Archaeutatus sp.; Parutaetus; Prozaedyus; Peltephilidae: Peltephilus undulatus; Glyptodontidae, Glyptatelinae indet.; Cingulata incertae sedis: Machlydotherium ater; Phyllophaga: Pseudoglyptodon; Notoungulata, ‘Notohippidae’, ‘Rhynchippinae’: Rhynchippus pumilus; ‘Rhynchippinae’ indet.; Interatheriidae: Eopachyrucos pliciferus, Proargyrohyrax curanderensis; ‘Archaeohyracidae’: Pseudhyrax eutrachytheroides?; Leontiniidae: Leontinia gaudryi?; Isotemnidae indet.; Litopterna, Proterotheriidae indet. Although the presence of Leontinia and Rhynchippus might support a Deseadan age for these levels, the high diversity of xenarthrans and many groups of tipotheres (Interatheriidae and Archaeohyracidae) could indicate a Tinguirirican mammal Age. Moreover, this association could represent an equivalent fauna to that registered in levels from La Cantera (Gran Barranca), with a radiometric estimated age of ca. 30 Ma, which would indicate a post-Tinguirirican to pre-Deseadan age. From a paleobiogeographic point of view Barrancas Blancas would correspond to the most eastern Patagonian locality with Paleogene Fauna of the ages mentioned above.