Bite marks on early Holocene Tursiops truncatus fossils from the North Sea indicate scavenging by rays (Chondrichthyes, Rajidae)

Abstract

A number of Tursiops truncatus mandibles in the collection of fossil marine mammals in the Rotterdam Natural History Museum have marks consisting of several parallel linear grooves. These marks are also found on four atlas complexes, a scapula and on one vertebra. The hypothesis that they are bite marks and were caused by scavenging rays (Rajidae, Chondrichthyes) was tested with a real-life experiment using different shark and ray species, allowing them to scavenge on cow ribs as proxies for the dolphin bones. The bite marks of these animals were compared with the fossil marks and show that the fossil marks are most likely caused by scavenging rays.