ABSTRACT The Mylodontidae Scelidotheriinae (Mammalia, Xenarthra, Tardigrada) are a diversified clade of South American fossil ground sloths, with a wide geographic distribution, especially in high and middle latitudes. According to the last revision, the Quaternary diversity includes the genera Scelidotherium, Catonyx, and Valgipes. The clade Scelidotheriinae is well represented in the Pleistocene of the Tarija-Padcaya basin, and the first mention of these ground sloths correspond to the middle of the XIX Century. Since then, several species (i.e., Scelidotherium tarijensis, Scelidodon tarijensis, Scelidotherium capellini) have been reported as inhabiting the Tarija-Padcaya basin during the Pleistocene. Despite the abundance of fossil records of Scelidotheriinae in this area, no modern taxonomic revisions are available. In consequence, in this contribution a revision of the remains assigned to Scelidotheriinae from the Tarija-Padcaya basin is accomplished, and some biostratigraphic and geographic implications are discussed. Our results show that one single species (Catonyx tarijensis) can be recognized in the studied area, whereas a supposed smaller one (Scelidotherium patrium) actually corresponds to juvenile specimens of C. tarijensis.

New records of Glyptodon munizi Ameghino (a taxon up to now only known by partial remains of the dorsal carapace) are reported. In this sense, these new findings allow us to sustain the validity of this species and to give a more precise and comprehensive diagnosis and description. The main differences with the Lujanian species of the genus Glyptodon are: a) a bigger size; b) an elongated skull with a remarkably narrowing between the postorbital process of yugal and the supraoccipital crest, c) first molariform with a primitive shape, without a marked lobulation. In addition, a ventral plastron and a high number of facial osteodermes, are described for the first time. This taxon is limited to the Ensenadan Stage (Late Pliocene-Middle Pleistocene), while from a palaeozoogeographic point of view, all the reports are restricted to the Buenos Aires Province.

Se dan a conocer nuevos registros de Glyptodon munizi Ameghino (Cingulata, Glyptodontinae), del Ensenadense de la región Pampeana, especie hasta el momento sólo conocida sobre la base de restos parciales de la coraza dorsal. Los nuevos hallazgos permitieron confirmar la validez de la especie y aportar una nueva y más completa diagnosis y descripción. Difiere de las especies lujanenses por: a) el mayor tamaño general; b) un mayor alargamiento del cráneo y estrechamiento de la región comprendida entre las apófisis postorbitarias y la cresta supraoccipital; y, c) el primer molariforme de conformación más primitiva. También se verificó la presencia de un plastrón ventral y de un gran número de osteodermos faciales, ambas estructuras halladas en uno de los ejemplares. Estratigráficamente, esta especie está limitada al Ensenadense (Plioceno tardío- Pleistoceno medio), en tanto que geográficamente todos los registros están restringidos al área de la provincia de Buenos Aires.

In this paper, the authors report the remains of some taxa of Pleistocene mammals coming from Chaco Province, Argentina. These remains were classified as Glyptodon sp., Neosclerocalyptus cf. N. heusseri, Panochthus sp., Propraopus grandis, Megatherium cf. M. americanum, Megatherium sp., Scelidotherium cf. S. leptocephalum, Lestodon sp., Equus (Amerhippus) neogeus, Toxodon cf. T. gezi and Toxodon sp., Smilodon populator, Morenelaphus sp., Stegomastodon cf. S. platensis and Stegomastodon sp. It is possible to assign a Bonaerian-Lujanian age (middle Pleistocene-early Holocene) for this assemblage of mammals. Paleozoogeographically, the authors remark the similitude of the taxa here described and those reported for the pampean region, Santa Fe, Formosa, Paraguay and southern Bolivia. This situation permits to infer similar climatic conditions among these areas. On the other hand, a preliminary palaeofaunistic comparison with Chile shows some significative differences, specially with central Chile, while the southern and northern regions are more similar to the Argentinian Quaternary paleofauna.

Se da a conocer un conjunto de restos óseos de mamíferos pleistocenos provenientes de distintas localidades de la Provincia del Chaco, Argentina. El conjunto está integrado por Glyptodon sp., Neosclerocalyptus cf. N. heusseri, Panochthus sp., Propraopus grandis, Megatherium cf. M. americanum, Megatherium sp., Scelidotherium cf. S. leptocephalum, Lestodon sp., Equus (Amerhippus) neogeus, Toxodon cf. T. gezi y Toxodon sp., Smilodon populator, Morenelaphus sp., Stegomastodon cf. S. platensis, Stegomastodon sp. La asociación es referible al Bonaerense-Lujanense (Pleistoceno medio- Holoceno temprano). Desde el punto de vista paleozoogeográfico muestra gran similitud con aquéllas de igual antigüedad de la región pampeana, de la Provincia de Formosa, Paraguay y sudeste de Bolivia. Estas similitudes son atribuidas a una marcada homogeneidad ambiental. Por otro lado, una comparación preliminar con la paleomastofauna de Chile indica algunas diferencias significativas, fundamentalmente con respecto a la región central, mientras que hacia el sur y norte se observan mayores similitudes con la paleofauna cuaternaria de Argentina.