Diplodon

Abstract: The current knowledge about the Chilean freshwater bivalves is presented. The bivalves described at present are adscribed to two families: Hyriidae represented only by the genus Diplodon with two species (D. chilensis and D. solidulus) and Sphaeriidae represented by three genera: Pisidium with seven species (P. chilense, P. magellanicum, P. lebruni, P. observationis, P. meierbrooki, P. huillichum and P. llanquihuense), Sphaerium with two species (S. lauricochae and S. forbesi), and Musculium with two species (M. argentinum and M. patagonicum). Subgeneric and subspecific taxa are recognized for Hyriidae only. Pisidium chilense, P. huillichum, P. llanquihuense P. lebruni and D. solidulus are proposed as endemic species for Chile. It is allocated the geographic distribution of the species, the taxonomic implications of the phenotypic variations exhibited by hyrids, the causes of the declination of the populations and the lack of knowledge in both families are analyzed. Specialists on the field and the available collections are listed.

Abstract: Bivalve molluscs of Sao Marcos locality, Medium Uruguay River Basin, Brazil. To verifi cation of quali-quantitative it has been accomplished collected of bivalve molluscs during the period of twelve months, together with analysis of some abiotic variables in the middle care of Uruguay river, situated in Sao Marcos, Uruguaiana municipality. The place where the collects has been accomplished, were divided in three distinct spots, considerating the substract type predominant; sand, rock and mud. The individuals were collected usinghands and with. The selection screen aid, of 0.8mm size net and were conserved in a dry environment. They had been collected a total of 1,022 units of bivalves, wich belong to 12 taxa, being that of these only specimensCyanocyclas limosa and Diplodon parallelopipedon had been captured alive (tanatocenosis). It had great quantitative predominance of Corbicula fluminea and Diplodon uruguayensis. With exception of bivalves invading,the too much species had been collected only in the slimy substratum. Other species occurrence were Mycetopoda siliquosa and Anodontites trigonus, there two species a vulnerable to extinction in Rio Grande do Sul.

Abstract: New species of Diplodon Spix (Bivalvia, Unionidea) from the Middle Jurassic (La Matilde Formation), of Santa Cruz province, Argentina. Two new species, Diplodon simplex Morton n. sp. and Diplodon matildensis Morton n. sp. are described from the Middle Jurassic La Matilde Formation of Santa Cruz province, Argentina. These findings reinforce some ideas of the southern origin and dispersal of this group of bivalves. Additionally, the gastropod Potamolithus sp., associated with Diplodon, is briefly described.