Bioerosion traces by endolithic foraminiferans on Recent and Miocene oysters from Patagonia (Argentina)

ROMERO, M. V.; FERRERO, L.; BREZINA, S.; BREMEC, C.; CASADIO, SILVIO

General Roca

Congreso; 11 Congreso de la Asociación Paleontológica Argentina; 2016

Asociación Paleontologica Argentina

This study reports the identity of foraminiferans within rosetted borings assigned toSemidendrina pulchra Bromley, Wisshak, Glaub, Botquelenon, 2007, on the Recent oysterOstrea puelchana d'Orbigny, 1842, from San Matías Gulf (Patagonia, Argentina).Foraminiferan tests were removed from their bioerosion traces and, SEM (Scanning ElectronMicroscope) and SEM-EDX (energy dispersive X-ray) analyses were performed in order toassess their morphological and compositional features. The same rosetted borings wererecognized on the Miocene species Ostrea alvarezii d'Orbigny, 1842, from Puerto MadrynFormation (Patagonia, Argentina, MPEF-PI 5001-5376). S. pulchra on Recent and Mioceneoysters were studied with SEM in low vacuum mode. The traces were clustered in largenumbers on valves of both oysters. They consisted of a fan-shaped plexus of galleries, whichwere connected to the surface by perforations and, for the other side, with a main chamberwhere an individual specimen was nested. These rosetted borings are dwelling or nestingtraces produced by a weakly agglutinated foraminiferan assigned tentatively to genusTrochammina Parker and Jones, 1859. Miocene