CASADIO Silvio Alberto
congresos y reuniones científicas
Boring and encrusting barnacles through the Cretaceous/Paleogene boundary in northern Patagonia (Argentina)
Santa Rosa
Simposio; II Simposio Latinoamericano de Icnología; 2013
Institución organizadora:
Conicet y Unlpam
Barnacles are found in all oceans and estuaries, distributed from the tropics to the poles and from the intertidal zone to the abyssal depths. The radiation of barnacles is reflected by the variety of substrates that they are able to attach or bore, including biogenic and abiogenic substrates. The group is considered successful in terms of abundance and diversity. Barnacles have adaptive strategies to occupy and persist in widespread, diverse, and physiologically challenging environments. Little is known about this group as a fossil constituent of encrusting and boring communities associated to hard substrates from middle latitudes in Southern Hemisphere. The changes in these communities during episodes of extinction like those that occurred during the Cretaceous/Paleogene boundary are almost unknown. This work reports the encrusting and boring barnacles associated to oysters from the K-Pg boundary and their changes in their relative abundances. The barnacles and their traces studied here come from 1.174 oysters specimens belonged to Pycnodonte (Ph.) vesicularis, Turkostrea damboreneae and Amphidonte mendozana (late Maastrichtian), Gryphaeostrea callophylla, Pycnodonte (Ph.) burckhardti and Turkostrea argentina (early Danian) and Ostrea wilckensi, Pycnodonte (Ph.) sarmientoi and Cubitostrea ameghinoi (late Danian). The barnacles identified on the oyster shells belong to Acrothoracica (boring barnacles) and Thoracica (encrusting barnacles). Boring barnacles are represented by traces assigned to Rogerella De Saint-Seine, 1951. This trace does not show significant differences in the relative abundance at the K-Pg boundary, however, during the late Danian it was more common. The encrusting barnacles were assigned to Verruca Schumacher, 1817. Verruca spp. and their traces Centrichnus ispp. are absent during the late Maastrichtian, show very low abundance in the early Danian and high abundance in the late Danian. These results suggest that boring barnacles were not affected by the environmental disturbances at the K/Pg boundary. However during the late Danian it was recorded a significant increase of encrusting barnacles. This change after the earliest Danian correlates with an increase in the number of species of corals, mollusks, echinoids and crabs derived from low latitudes, reflecting higher seawater temperatures spreading south.