Eggs for breakfast? Analysis of a probable mosasaur biting trace on the Cretaceous echinoid Echinocorys ovata Leske, 1778

Abstract. Fossil biting traces (praedichnia) represent indirect evidence of predation and shed light on fossil predator–prey interactions and fossil food webs. Especially from echinoderm skeletons, biting traces are well known. Here, we describe the oral surface of a large Cretaceous (Maastrichtian) holasteroid echinoid Echinocorys ovata Leske, 1778 from Hemmoor (northern Germany) which exhibits four circular punctures arranged in a semi-circular arc. Whereas three of the punctures penetrated the skeleton, one puncture only just hit the margin of the echinoid test at the ambitus, leaving a long incision furrow in the skeleton. The punctures were not lethal to the sea urchin as is indicated by progressed skeletal regeneration and closure of the fractures. The overall appearance of the punctures suggests that they were produced during a single mechanical event, most likely by the biting action of the teeth of a large vertebrate animal. We analysed the shape and arrangement of the biting trace and conclude that it was probably produced by a marine reptile possessing a prognath tooth position, most likely by a globidensine mosasauroid. Our finding not only sheds light on mosasaur feeding behaviour and prey selection but also increases the knowledge of the food webs in the chalk sea ecosystem during the uppermost Cretaceous.