Drilling predation on Gryphus vitreus (Brachiopoda) off the French Mediterranean coasts

A total of 145 valves of Gryphus vitreus with naticid drillholes have been recorded from samples during 21 cruises in the Northwestern Mediterranean, out of about 30,000 empty valves. Drilling was lower than 1% in all stations, except in one station where it reached up to 25.5%. Selectivity of drillhole site by the naticid Euspirella pulchella seems to apply in G. vitreus as drillholes are mainly concentrated in the relatively meaty distal half of the shell, which is also the thickest part of the valve (about 0.6–2 mm). Attacks occur generally on the ventral valve (86.2%) according to the life position of Gryphus. The predation pressure on G. vitreus by drilling appears exceptional in that it has hardly any influence on the evolution of the species. This contradicts several previous statements on the fossil record.