Trilobite sclerites as attachment surface for Emsian tabulate corals of Hamar Laghdad (Anti-Atlas, Morocco)

摘要

At the 'Red Cliff' in Hamar Laghdad, the latest Emsian strata yielded an assemblage that is partially silicified and thus was weathered perfectly out of the marly sediments. Thereby, previously overlooked morphological details of fossils may be revealed. Here, we document cases where colonies of ?Pterodictyum sp., a small tabulate, grew on exuviae of the head shields of a harpetid and a phacopid trilobite. We suggest that coral larvae settled on the trilobite exuviae, or, less likely, on dead individuals (hence they were epicoles). Trilobite remains were among the larger skeletal elements that were available and thus forming benthic islands on surfaces full of mostly smaller debris; it is likely that the size of these fragments, their sculpture and stability against currents favoured them as places for coral larvae settlement.