Echinoid burrow Bichordites monastiriensis from the Oligocene of NE Italy

Several specimens of trace fossil Bichordites monastiriensis were discovered in two shallow water Oligocene sandstone beds from Valsugana (Trentino, NE Italy) representing the oldest documented occurrence for this ichnospecies. They are grazing−crawling (pascichnion−repichnion) structures and are occasionally associated with enlarged structures that can be interpreted as resting traces (cubichnia) and assigned to the ichnogenus Cardioichnus. The resulting Bichordites–Cardioichnus compound trace fossil is here described for the first time. In the basal part of some specimens, skeletal remains of Eupatagus ornatus were found in life position. This founding enables to widen the spectrum of known Bichordites tracemakers. Exceptional conditions of preservation of one specimen extending in two beds recording different environmental conditions gave an opportunity to document the effects of various taphonomical histories on the preservation of this traces.