Ichnology of fossil oysters (bivalvia, ostreidae) from the southern Brazilian coast

Ichnological features over fossil oysters from southern Brazilian coast are described herein. In the deposits Ostrea puelchana d’Orbigny, 1841 is the dominant oyster, followed by O. equestris Say, 1834 and Crassostrea virginica Gmelin, 1791. Although these taxa are found along the entire coast, they exhibit some geographical variations regarding the presence of borings. The most conspicuous ichnogenera are Caulostrepsis and Entobia, with Gastrochaenolites being common in fossils from the central sector of the coast, and scarce in the southern one. Maeandropolydora and incrustations (made by fouling organisms, e.g. cirripeds and bryozoans) are scarce. Most of the borings are found on the external side of the valves which suggest a dominant bioerosion activity during the life span of the organisms