Redescription ofMactra bonariensisPhilippi, 1893 and designation of a neotype

During an ongoing revision of the Paraná Formation fauna of Argentina, the taxonomic status of Mactra bonariensis Philippi, 1893, was reassessed. The morphological characters of M. bonariensis provided in the original description and illustration do not allow clear delimitation of the species. The absence of type material of this species, coupled with difficulties in resampling the type locality due to urbanization, necessitates designation of a neotype. No records of this taxon were found in palaeontological and malacological collections. However, material collected from the Paraná Formation at 'La Juanita' (Entre Ríos, Argentina) comes from beds equivalent to those exposed at the locality from which Philippi described the original material. As this species may be confused with Quaternary and extant species from the region, a redescription is provided and a neotype designated. Fil: Pérez, Leandro Martín. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleozoología Invertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Signorelli, Javier Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina