First record of land gastropods of the family Charopidae in the Early to Middle Miocene from Santa Cruz Province, Southern Patagonia, Argentina (Gastropoda Pulmonata: Stylommatophora: Charopidae)
Rodriguez, Pablo E.; Miquel, Sergio E.; Tauber, Adán A.; Krapovickas, Jerónimo M.
The Miocene fauna of land gastropods from Patagonia is still poorly known. This work presents the first record of a land pulmonate gastropod belonging to the genus Stephadiscus (Mollusca: Stylommatophora: Charopidae), in the Santa Cruz Formation (Argentina, early-middle Miocene). The importance of this find is analyzed in the geological and paleontological contexts and its paleoclimatic and paleogeobiogeographical significance is discussed. The previous fossil record of this Formation has provided indicators of very different climatic and environmental conditions, viz. a trend from warm, humid conditions and arboreal environments to more arid conditions and more open environments. These paleoenvironmental reconstructions have been based on sedimentological studies, functional morphological analyses of different vertebrate species, their phylogenetic relations, and cenograms of mammal communities. Accordingly, the presence of Stephadiscus sp. at fossiliferous level 6 of Santa Cruz Formation indicates a setting of humid environmental conditions at least for the early-middle Miocene, with development of shrubby and forest vegetation, which is consistent with humidity and environmental stability conditions interpreted from the record of paleochannels, floodplains and the most mature paleosol found in the Atlantic coast south of Coyle River.