Predatory boreholes in Tournaisian (Lower Carboniferous) spiriferid brachiopods

A brachiopod fauna from the uppermost part of the Tournaisian Tournai Formation (Belgium) contains an undetermined species of Crurithyris (Spiriferida, Ambocoeliidae), which displays numerous bored shells. About 8% of the 432 specimens with conjoined valves display single, small (< 1 mm) boreholes, which are smooth-sided, cylindrical or weakly conical, circular to slightly elliptical in plan view, perpendicular to the shell surface and generally complete. Of the 35 bored articulated specimens, 27 were drilled on the ventral valve. Most of the boreholes are located in the posterior half of the shell, and no case of edge-drilling has been observed. The boreholes were drilled by a predator, or possibly a parasite, which selected individuals greater than 2.5 mm long. Crurithyris sp. may have represented an attractive (in terms of energy cost) and easy target for a small-sized predator because of its thin shell and ornament of minute spines.