Continental mollusk assemblages from the Quaternary of Uruguay

Abstract

Only a few studies on Quaternary continental mollusks of Uruguay have been published over the last few decades. Despite the high occurrence of this group in many of the Late Pleistocene outcrops of the country, all of them are better known for their classic Ice Age mammal assemblages. To overcome this situation, 23 localities were sampled from two lithostratigraphic units: the Sopas and Dolores formations. The identified species are included in the families Sphaeriidae, Cyprinidae, Mycetopoda, Acridae (freshwater bivalves); Ampullariidae, Cochliopidae, Tateidae, Chilina, Physidae, Planorbidae (freshwater gastropods); Scolodontidae, Succineidae, Charopidae and Bulimia (terrestrial gastropods). As a result of these new samplings, the Sopas Formation mollusk species count increased from 20 to 29 species, and the Dolores Formation from six to 29 species. Seventeen of these species are new records for the Quaternary of Uruguay, and eight for the Quaternary of South America. Two bivalves, five freshwater gastropods, and a new terrestrial gastropod were added for the Sopas Formation; and for the Dolores Formation, four new bivalves, 14 new freshwater gastropods, and five new terrestrial gastropods. The Dolores Formation has been the most understudied unit until now, increasing here its biodiversity to 23 species. These new records of freshwater and terrestrial gastropods, increase the biodiversity and biogeographical range of the continental mollusks of the Late Pleistocene-early Holocene of the region. In addition, new AMS 14C ages were obtained for both lithostratigraphic units, framing the age of the mollusk assemblages for both formations in the a maximum range of 13,000–48,000 years before the present.