Moluscos bivalvos de las facies cuarcíticas del Ordovícico Inferior centroibérico

Abstract

Some scarce and bad preserved bivalves have been described from few localities lying at the upper part of the Armorican quartzite facies in Central Spain. Middle Arenig faunas include two palaeotaxodont forms (Praenucula oehlerti and Cardiolaria sp.), and two different palaeoheterodonts (Modiolopsis sp. and ?Actinodontoida indet.). Previous reports of other Arenig bivalves, especially actinodontoids, from coeval quartzites of northwestern, Central and northeastern Spain, as well as from Central Portugal, have been also briefly examined. The Iberian faunas show close affinities with the well known Arenig assemblages from the «Grès armoricain» of Western France, and add new data for the scenic reconstruction of the Lower Ordovician bivalve radiations on the northwestern Gondwanan shelves