Abstract The fragmentary remains of a mosasaur discovered in the Smoky Hill Chalk Member (Late Coniacian) of the Niobrara Chalk of Gove County, Kansas, U.S.A., preserve a number of injuries consistent with scavenging by two species of lamnid shark. The mosasaur remains (FHSM VP-13746) were identified as cf. Ectenosaurus clidastoides and consisted of a continuous series of 21 dorsal vertebrae. No evidence was found of the anterior neck and skull, limbs or caudal vertebrae. A single cervical vertebra was located in front of the first dorsal and one posterior dorsal vertebra had been fractured prior to burial. Although still associated with the vertebral column, most of the ribs were severed or otherwise damaged. No residual of the cartilaginous sternum was found. Deep bite marks on several of the vertebrae, severed ribs and the tip of a large, embedded tooth are interpreted as evidence that the lamniform shark, Cretoxyrhina mantelli, had fed on the mosasaur remains. The spacing of the individual tooth marks (3 cm) indicate the bites were from a very large (estimated 5 m) shark. Lesser damage, including serrated bite marks and scrapes indicated that another shark species, Squalicorax falcatus, had also been involved. This specimen is important palaeoecologically because it documents a predator-prey relationship between these two species of sharks and mosasaurs, and because it provides further evidence that Cretoxyrhina and Squalicorax fed on large vertebrates in the Late Cretaceous seas of North America.


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