Astrapotheres from Cañadón Vaca, middle Eocene of central Patagonia. New insights on diversity, anatomy, and early evolution of Astrapotheria

KRAMARZ, A.; BOND, M; CARLINI, ALFREDO A.

PALAEONTOLOGIA ELECTRONICA

COQUINA PRESS

Lugar: New York; Año: 2019 p. 1 - 22

1094-8074

Astrapotheria is one of the most emblematic groups of endemic South Americanungulate-like extinct mammals, traditionally compared with modern tapirs and rhinos.Oldest astrapotheres are known from the early Eocene Itaboraian fauna (Brazil), butthe earliest diverse astrapothere assemblage is known from the middle EoceneCañadón Vaca Member of the Sarmiento Formation exposed at Cañadón Vaca (Vacansubage of the Casamayoran Land Mammal Age), in central Patagonia, Argentina. Previousreports of astrapotheres from Cañadón Vaca included Trigonostylops, Tetragonostylops,Albertogaudrya, and Scaglia, but only the record of the latter was unequivocal.New materials from Cañadón Vaca described herein confirms the occurrence of Trigonostylops(T. wortmani) and of Tetragonostylops (likely represented by a species differentfrom the nominal species from Itaboraí). Additionally, two other taxa are identified:the former, described as cf. Scaglia cf. kraglievichorum, is represented by a partialskull with an unusual combination of cranial characters, and could correspond to anadult of Scaglia kraglievichorum (known by a juvenile skull); the other taxon is representedby a partial mandible with distinctive osteological and dental features, but thepossibility of its belonging to Scaglia cannot be discarded. The occurrence of Albertogaudryain Cañadón Vaca could not be confirmed by the examination of the new andprevious collections. Astrapotheres from Cañadón Vaca show a wide morphologicaldisparity of cranial designs, but all consistently share long, unreduced nasals, thus thepresumed possession of a short tapir-like proboscis only typifies the post-Casamayoranastrapotheres.