Echiura from the Pennsylvanian Essex Fauna of northern Illinois

Abstract

The first unequivocal fossil echiuran, Coprinoscolex ellogimus gen. et sp.n., is described from the Middle Pennsylvanian Francis Creek Shale of the Mazon Creek area of northeastern Illinois. Specimens are whole-body impressions within siderite concretions. They show anterior proboscides, cigar-shaped trunks, convoluted alimentary canals, and cylindrical pellets. Lack of setae suggests classification in the Family Bonelliidae. Coprinoscolex was most likely a marine deposit-feeder, either crawling over the sediment surface or burrowing to shallow depths while ingesting sediment. While this occurrence does not confirm or deny an annelidan ancestry for the Echiura, it indicates that by the Pennsylvanian, echiurans were unsegmented and essentially modern in form.