Abstract

TAUBER (H), Adán A.. Fossil mammals and age of the Salicas Formation ( late Miocene ), sierra de Velasco , La Rioja province , Argentina. Ameghiniana [online]. 2005, vol.42, n.2, pp.443-460. ISSN 1851-8044.

Bone remains of fossil mammals from the Salicas Formation, appearing in the northern end of Sierra de Velasco, La Rioja province, Argentina, are reported. This stratigraphic unit was previously assigned to the Pliocene, Upper Pliocene and to the Late Miocene. It is made up of clayey sandstone, friable in general, brownish in the lower layers, and reddish brown in the upper levels. There are also intercalated paleosoil layers, and fossiliferous conglomerates of fluvial origin. Among the findings, anuran, turtle and mammal fossils are reported. The main species are: Macrochorobates scalabrinii Scillato Yané, Proeuphractus limpidus Ameghino, Chaetophractus sp., Eosclerocalyptus planus Castellanos, Neophanomys biplicatus Rovereto, Lagostomus ( Lagostomopsis ) cf. pretrichodactyla Kraglievich, Orthomyctera andina Kraglievich, Potamarchus sp., Protypotherium sp., Pseudotypotherium sp., Hemihegetotherium cf. Torresi Zetti and cf. Tremacyllus . All these correspond to the Late Miocene ("Huayquerian" mammalian age). This association is different from all the other findings in the Pampean region, hence its significance is discussed. Then, the hypothesis of a Late Miocene latitudinal retraction of the genus Protypotherium from the Pampean region towards the North, is proposed. Some of the species were also reported from El Jarillal Member of the Chiquimil Formation and from the lower part of the Andalhuala Formation ("Huayquerian") in Catamarca province, with which the bearing sediments are correlated.

Keywords : Salicas Formation; Mammals; Late Miocene; La Rioja Province; Argentina.