"Bivalvos del Pérmico Inferior de la Formación Bonete, Sierras Australes (provincia de Buenos Aires, Argentina)"

Abstract

"A bivalve fauna from the Pillahuincó Group in Sauce Grande Basin (Buenos Aires province. Argentina), first discovered and described by Harrington, is here revised and illustrated. A reassessrnent of the taxonomy, provincial affinities and age of the fauna reinforces its Gondwanic character. This feature denotes its probable correlation with Early Permian faunas of Brazil, Australia and South Africa. Eight species of Bivalvia are described and ilIustrated. Two of them: Heteropeeten sp. and Myonia sp. are described for the first time for the Bonete Formation. Other six species are revised: Leptodesrna (Lcioincria) bonaerensis (Harrington), Leptodesma (Leiopteria) dutoiti (Harrington), Atomodesma (Aphanaia) orbiru::; 11I17(Harrington). Pronuitilus acinaajormis Harrington, Stuichburia argeniinensis Harrington, Allorisma illfleetovclltris Harrington. The association also contains brachiopods, gastropods and plant remains. Comparisons with genera registered from Brazil, Australia, New Zealand and United States are established. The recorded bivalve assemblage fram the Bonete Formation suggests a possible faunal connection with similar assernblages from the Rio do Sul and Rio Bonito Formations in the Parana Basin (Brazil). This possible paleobiogeographic relationship between the two basins, would be favored by similar environment conditions. The record of Eurijdesma, Deltopecien and Atomodesna in the Bonete Formation indicates a Late Asselian-Artinskian age for the bivalve fauna. The occurrence of the brachiopod Tioertonia in this formation, the faunal affinities with Australian and Brazilian faunas, and the paleofloristic assemblage, are additional evidences which support this age."