First record of Arctotherium (Ursidae, Tremarctinae) in northwestern Argentina: paleobiogeographic significance.

DANIEL GARCÍA LÓPEZ; PABLO EDMUNDO ORTIZ; MARÍA CAROLINA MADOZZO JAÉN; SEBASTIÁN MOYANO

JOURNAL OF VERTEBRATE PALEONTOLOGY

Society of Vertebrate Paleontology

Lugar: Deerfield, Illinois, Estados Unidos; Año: 2007

0272-4634

Here we describe the first remains of Arctotherium from Late Pleistocene deposits of northwestern Argentina. An almost complete left mandible (PVL 6158) of a very old individual was found 5 km south of El Rodeo, Ambato Department, Catamarca Province, Argentina, within a layer constituted by massive silts in loessic sediments. The most striking difference between PVL 6158 and all the recognized species of Arctotherium, except A. wingei, are its slenderness and small size. The morphological similarities between the specimen from Catamarca and the type of A. wingei, from Tarija valley, Bolivia, as well as geographical and environmental patterns at both localities, suggest the presence of an Andean group of species of Arctotherium distinguishable from those found at lowland and eastern regions of South America. Until new remains are found, we do not assign PVL 6158 to any known species of Arctotherium and refrain from proposing the existence of a new taxon. The specimen from El Rodeo constitutes the first mention of a tremarctine bear from the northern region of this country. Furthermore, it represents the first record of a bear, fossil or living, from this region. The presence of populations of Arctotherium in this area could be related to some of the last glacial events of the Late Pleistocene that produced arid and cold environment in northwestern Argentina.