INVESTIGADORES
FORASIEPI Analia Marta
congresos y reuniones científicas
Título:
Potamolithus windhauseni (Parodiz, 1961) (Gastropoda-Hidrobiidae) in Los Alamitos Formation (Campanian-Maastrichtian) from Río Negro Province, Argentina
Autor/es:
FORASIEPI, A. M.; LOPEZ ARMENGOL, M. F.
Lugar:
Buenos Aires
Reunión:
Simposio; VII International Symposium on Mesozoic Terrestrial Ecosystems; 1999
Institución organizadora:
Museo Argentino de Ciencias Naturales Bernardino Rivadavia
Resumen:
In 1961 Parodiz described a freshwater snal named Valvata windhauseni (Valvatidae) from the Jagüel Formation (Maastrichtian) of Río Negro Province. Eight years later, he considered that this species could be included in the genus Potamolithus, although he did not offer reasons for that change. Many specimens of fossil freshwater snails collected from different levels of Los Alamitos Formation (Campanian-Maastrichtian), Río Negro Province, are assigned here to Potamilithus because they exhibit trochoid shell, smooth surface, and occasional growth lines and umbilical area, features found in extant species of Potamolithus. The inclusion to the windhauseni species in Potamolithus is supported for the subsutural angle and a basal carina over their last whorl. Differences, lacking taxonomic significance, can be produced by sexual dimorphism or trematode´s parasitism, as females and parasited specimens are bigger in living populations. In this 1987´s work about the stratigraphy and paleoenvironment of Los Alamitos Formation, Andreis hypothesized that the dominant regime of this unit was preferentially lacustrine than fluvial, and the water was brackish rather fresh, pointing out that the absence of pyrite-bearing anoxic facies and abundant bioturbation were indicating well oxygenated waters. This hypothesis is also supported by the presence of Potamolithus.