Paleoethologic implications of Zoophycos from Late Cretaceous and Paleocene limestones of the Venetian Prealps, northeastern Italy

Abstract

Large specimens of Zoophycos are abundant in Paleocene pelagic limestone successions in the vicinity of Feltre and Belluno, in northeastern Italy. These burrow systems are familiar examples of the strongly ribbed, downwardly spiralling version of the ichnogenus, containing well-developed primary and secondary lamellae, marginal tunnels, and poorly preserved axial structures. Some of the specimens contain fecal pellets rich in non-carbonate mud and carbonized phytodetritus, suggesting surface deposit feeding and organized subsurface storage of fecal material by the Zoophycos producer. Other examples of the burrows record a departure from the normal behavioral pattern in the form of conspicuous radial tunnels that diverge from the axial region, cut across structural elements, and follow the laminae exactly to the outer margin. This special feature of fully developed Zoophycos appears to represent the last time the trace producers recycled the banks of fecal material, possibly during long intervals of meager food supply at the deep ocean floor.