Showing papers in "Palaeontographica Abteilung A-palaozoologie-stratigraphie in 1987"

Early Jurassic Bivalvia of Argentina. Part 2: superfamilies Pteriacea, Buchiacea and part of Pectinacea

Abstract: A detailed systematic study has been made of 22 species of Early Jurassic bivalves belonging to 17 genera and subgenera and to 11 families of the superfamilies Pteriacea, Buchiacea and Pectinacea. Of these, two subgenera: Gervilleioperna (Gervilletia) and Weyla (Lywea) and six species: Aguilerella neuquensis, Bakevellia (Neobakevellia ?) pintadae, Gervillella araucana, Pulvinites (Hypotrema) liasicus, Otapiria *) Author’s address: Dr. S. E. D amborenea, Division Paleozoologia Invertebrados, Museo de Ciencias Naturales de La Plata, Paseo del Bosque, 1900 La Plata, Argentina. Palaeontographica Abt. A. Bd. 199 15 neuquensis and Otapiria ? frenguellii, are new. The research was based mainly upon the author's own material collected W 11 from about 50 fossiliferous localities in the provinces of San Juan, Mendoza and Neuquen (Argentina). ® \" Some of the genus-group taxa are recognized and illustrated for the first time in the Early Jurassic of Argentina and this stud has also revealed the oldest pulvinitids so far worldwide. Although the bivalves studied reveal, as a whole, strong affinities with tv ' 11 T thvan ones at the generic level, most of the species have a restricted geographical distribution within the South American Andes Some of the species are nonetheless indistinguishable or very closely related to European forms. The understanding of some of the genera, such as Aguilerella C havan and Weyla Bohm, has been substantially improved, whilst the phylogenetic relationships of some of them are also discussed. An outline of the palaeoautecology of each species is provided, too. Knowledge about the stratigraphical range of many species has been significantly improved and some of them (as in Weyla and Posidonotis Losacco) are shown to be stratigraphically useful. Palaeobiogeographical data analysis of genera such as Weyla, Posidonotis and Eopecten D ouvillE strengthens the available evidence favouring a faunal exchange between the east-central Pacific and the western Tethys during Early Jurassic times.