Los bivalvos carboníferos y pérmicos de Patagonia (Chubut, Argentina): Parte IV: familias Aviculopectinidae, Deltopectinidae y Schizodidae

Resumen. En este trabajo se realizo un exhaustivo analisis sistematico de la fauna de bivalvos del Paleozoico Superior, provenientes de diferentes niveles fosiliferos de la cuenca Tepuel-Genoa (provincia del Chubut, Argentina). En esta cuarta parte se detallan los resultados obtenidos en relacion a los representantes de las familias Aviculopectinidae, Deltopectinidae y Schizodidae. La abundancia de ejemplares y su buena preservacion permitieron describir e ilustrar nueve especies. Entre ellas se reconocen tres especies nuevas: Limipectenherrerai nov. sp., Streblopterialagunensis n. sp. y Streblopteriaminuta n. sp.; y dos nuevos registros: Aviculopecten sp. y Aviculopecten? sp. Con relacion a las especies ya conocidas para la cuenca, debido al hallazgo de nuevo material se han enmendado la diagnosis y ampliado la descripcion y distribucion geografica de Orbiculopectenparma Gonzalez y Schizoduspaucus Gonzalez. Estas formas han sido minuciosamente comparadas con formas de otras comarcas. Se discute, ademas, otro registro de Schizodus sp. Abstract. CARBONIFEROUS AND PERMIAN BIVALVES FROM PATAGONIA (CHUBUT, ARGENTINA). PART IV: FAMILIES AVICULOPECTINIDAE, DELTOPECTINIDAE AND SCHIZODIDAE. A thorough systematic analysis is performed on the bivalve fauna of the Upper Paleozoic of the Tepuel-Genoa Basin (Chubut Province Argentina), as a contribution to the knowledge of early Permian faunas of Argentina. This fourth part comprises the families Aviculopectinidae, Deltopectinidae and Schizodidae, of which abundant well preserved specimens allowed the recognition of three new species, Limipectenherrerai nov. sp., Streblopterialagunensis n. sp. and Streblopteriaminuta n. sp. Two new records of Aviculopecten sp. and Aviculopecten? sp. are included too. On the basis of new material from the Tepuel-Genoa Basin, the diagnoses of Orbiculopectenparma Gonzalez and Schizoduspaucus Gonzalez are emended. In addition, the descriptions of these and other previously known species are supplemented by new information and their geographical ranges are expanded. Detailed comparisons of all species with taxa from other regions are also provided. A new record of Schizodus sp. is discussed too.