New toxodontid (Notoungulata) from the early Miocene of Argentina: the extra-Patagonian fossil record

ANALIA FORASIEPI; ESPERANZA CERDEÑO; MARIANO BOND; GABRIELA I. SCHMIDT; MAXIMILIANO NAIPAUER; FIONA R. STRAEHL; AGUSTIN MARTINELLI; ALBERTO GARRIDO; MARK SCHMITZ

PALAEONTOLOGISCHE ZEITSCHRIFT

SPRINGER HEIDELBERG

Lugar: HEIDELBERG; Año: 2015 vol. 89 p. 611 - 634

0031-0220

We describe a new toxodontid species, Nesodon taweretus sp. nov., from the Aisol Formation in Mendoza Province, central-western Argentina. Nesodon is a frequently found Toxodontidae, part member of the Notoungulata, an extinct endemic group of Cenozoic South America mammals, ecologically similar to current hoofed ungulates. The holotype of N. taweretus sp. nov. is a skull and we tentatively assign some mandibular fragments and postcranial bones. Nesodon taweretus sp. nov. differs from the other Neosodon species in several cranial and dental features and close comparisons were made with the Patagonian Nesodon imbricatus, common in the Santa Cruz Formation (Santacrucian Age, early Miocene). The material is has a similar size to N. imbricatus, but the body mass estimations suggest a lighter animal of about 450 kg. The histological sections of the ulna demonstrate a well vascularized bone with heavily remodeled parallel-fibered, lamellar and woven bone. The phylogenetic analysis groups N. taweretus sp. nov. with other species of Nesodon. The absolute age of the Aisol Formation has been established in 19.5 Ma (Burdigalian) by means of U-Pb, which places the unit in the latest early Miocene and the vertebrate association in the Santacrucian Age. Latitudinal separation between Mendoza and Patagonia in the south would have favored taxonomic differences as reflected by the species of Nesodon.