About the contact pads of Gryphaea Dilatata Sowerby (Dysodonta, Bivalvia) from the Oxfordian deposits of the Nizhnie Mnevniki (Moscow)

Abstract

The epibiosis’s features of the Oxfordian oysters Gryphaea dilatata Sowerby from Nizhnie MnevniH (Moscow) are first studied. The oysters used the attachment as a way to root to the substrate. The significant variety of the contact pads is revealed, indicating the deposition of the oysters on different hard objects, supporting the hold and stability of the epibiont. The objects of the attachment (contact pads) were lithosubstrate and biosubstrate approximately in equal proportions. The oysters were poor specialized in the lithosubstrate choice. The objects of the attachments within the biosubstrate were only scalped ammonites (78,5%) and bivalves (21,5%). Cases of the attachments of the Gryphaea oysters to the concrete species of the fossils are not revealed. The general analysis shows, that the oysters preferred to root both at elevated sites (44,4%) and at the depressions of the substrate (37 %), however did not like the flat surfaces (18,6%). The largest scars were formed in cases of the attachment to the elevated sites. The research of the contact pads of the Gryphaea oysters revealed more obvious picture of the composition of the Oxfordian biota at this location. The presence of the bivalves Oxytoma, Pholadomya and Trigonia is distinguished, but their remains are not existed. The twenty four studied specimens are illustrated.