INVESTIGADORES
ALIOTTA Salvador
congresos y reuniones científicas
Título:
Borings and Etchings of Holocene Micromolluscs in the Bahia Blanca Estuary, Argentina.
Autor/es:
FARINATI E.; ALIOTTA S.; SPAGNUOLO, J.
Lugar:
Trelew
Reunión:
Congreso; First International Congress on Ichnology (Ichnia 2004).; 2004
Institución organizadora:
Museo Paleontológico Egidio Feruglio
Resumen:
Fossil traces related with the organic activity are useful to understand the past coaction phenomena. This activity reflects boring and etching behaviours that respond to feeding and dwelling needs. In spite of their small size, micromolluscs (gastropods and bivalves) also are affected by bioerosive activity of organisms on their valves. Sandy shell accumulations, at levels of down to 6-7 m above mean sea level were deposited subparallel to the present coast. Of 107 molluscs species found in Holocene sand shell ridges, 35% (38 species) belong to micromolluscs. Only, 19 species shows bioerosion on their valves. Among predation structures (Praedichnia) are borings due to predatory activity by gastropods naticids and muricids. The holes are circular or subcircular and truncated cone shape. Over gastropods valves there are complete holes and there is always only one, while over the bivalve valves are frecuent multiples and uncompleted borings. These borings are being assigned to Oichnus simplex Bromley and Oichnus paraboloides Bromley. Another fossil traces (Domichnia) are the etchings made by cheilostome bryozoans. The pits have elliptical or pear shaped uniserially arranged over micromolluscs valves and being assigned to Leptichnus dromeus Taylor, Wilson and Bromley. Micromolluscs show taphonomic signatures that make evident the environmental conditions that affected them during their permanence on the sea bottom.