Burrowing trilobite caught in the act

A trace fossil associated with its assumed in situ maker, a holaspid specimen of the trilobite Agraulos ceticephalus (Barrande in Notice préliminaire sur le Systême Silurien et les trilobites de Bohême, Leipzig, 1846), is reported from the middle Cambrian Buchava Formation (Drumian Stage) of the Skryje-Tyřovice Basin, Czech Republic. The ichnofossil is preserved on the surface of a mudstone, behind the posterior part of the intact trilobite exoskeleton; this natural association is interpreted as mortichnia. Possible mode of life and feeding strategy of the trilobite genus Agraulos are discussed. For the association of a fodichnion with its producer preserved in situ (atop, in, or at the end of its trace fossil), the designation fodichnial association is proposed.