A new resting trace of echiuran worms from the Paleocene turbiditic deposits of the Northern Apennines and the Polish Outer Carpathians

Abstract

A new trace fossil, Cochlearichnus tumidus igen. nov. et isp. nov., is described from Paleocene deep-sea deposits of the Ropianka Formation (Magura Nappe, Polish Outer Carpathians) and the Pagliaro Formation (Northern Apennines, Italy). The trace occurs in fine-grained turbiditic sandstones and is preserved as a hypichnial convex semi-relief with a consistent spoon-shaped outline. Comparison with the body outlines of extant echiuran worms indicates that C. tumidus igen. nov. et isp. nov. represents a resting trace, most likely produced by a deep-sea echiuran inhabiting soft, muddy substrates. The structure was formed in mud and subsequently scoured and cast by turbiditic sand. The deposits bearing this trace fossil are characterized by the Paleodictyon ichnosubfacies within the Nereites ichnofacies, typical of distal parts of the turbiditic depositional systems.