Taphonomic and ethologic aspects of ichnology of the Maastrichtian of the type area (Upper Cretaceous, The Netherlands and Belgium)

Three rare ichnotaxa from the type area of the Maastrichtian Stage (Upper Cretaceous) are described, and their morphology and palaeoecological significance discussed; a fourth ichnotaxon shows an unusual mode of preservation. The infill of an articulated lithophagid bivalve (Meerssen Member, Maastricht Formation) preserves the distinctive firmground burrow Arachnostega gastrochaenae BERTLING, 1992. This is the first report of this trace fossil, probably generated by polychaetes, from the Cretaceous of northern Europe. The producer may have been grazing the inside of the bivalve shell while burrowing through its sediment infill. An indeterminate patellid limpet exhibits an additional example. Tubercles are recognised for the first time within the pits of Oichnus excavatus DONOVAN and JAGT, 2002b (Meerssen Member, Maastricht Formation), indicating they were probably the result of embedment rather than boring. The producing organism may have obtained a firmer attachment to the test by having abundant spines of the host echinoid embedded in its soft tissues. The boring Talpina cf. ramosa VON HAGENOW, 1840, commonly preserved as natural casts in decalcified shells, occurs as holes in the oyster Agerostrea ungulata (VON SCHLOTHEIM, 1813). Trypanites cf. solitarius MÄGDEFRAU, 1937, shows an unusually flattened morphology, in which the boring form has been determined in part by the distribution of organic layers within the shell of the oyster Rastellum macropterum sensu STENZEL, 1971 (Nekum Member, Maastricht Formation).