Ventral Bite Marks (Ichnospecies Bicrescomanducator rolli): Lethal Injuries on the Shells of Jurassic Ammonites

Ichnofossils are fossilized traces of the biological activity of ancient organisms, which often shed light on the paleoecological interactions of extinct animals. Mesozoic ammonites are no exception: holes in the walls of their body chambers, attributed to the ichnospecies Bicrescomanducator rolli Donovan et al., indicate predator attacks that were lethal for the ammonites. In this paper we describe numerous findings of B. rolli (also known as ventral bite marks) on ammonite shells from the Middle and Upper Jurassic of European part of Russia. These findings demonstrate that the pressure of predators, which left ventral bite marks on the ammonite shells, gradually increased and reached a maximum at the end of the Jurassic. These predators were most likely various coleoids, including the ancestors of modern squids and octopuses. Not only B. rolli but other rare ichnofossils were found on the Jurassic ammonites: Oichnus ovalis Bromley and Podichnus centrifugalis Bromley et Surlyk.