Scavenging by Sharks of the Genus Squalicorax in the Late Cretaceous of North America

Abstract

Diverse sources and types of evidence indicate that common Cretaceous selachians of the genus Squalicorax were the preeminent scavengers of vertebrate carcasses during Santonian and Campanian ages of the Late Cretaceous. Evidence considered comes from the eastern Gulf Coastal Plain and Western Interior of the United States. Direct, material evidence of scavenging includes a decayed mosasaur vertebral centrum and a hadrosaurian dinosaur metatarsal, each containing a Squalicorax tooth evidently embedded after the host's death. Abundant implicit evidence of scavenging includes Squalicorax bite marks and Squalicorax teeth associated with numerous marine tetrapod and fish remains, and at least one additional dinosaur. Many of these bite marks and tooth associations are with predaceous tetrapod taxa, well beyond the reasonable prey size of Squalicorax species. Inference of scavenging by Squalicorax is also based on comparative counts of selachian teeth in Upper Cretaceous deposits in the eastern Gulf of Mexico. Typical shark-tooth assemblages are dominated by lamnoid teeth, but at two well-studied localities containing the associated remains of large vertebrate carcasses, few shark teeth are found except those of Squalicorax, implying that these were shed during scavenging activity. Although it is not definitively proven that Squalicorax was an obligate scavenger, the longevity and cosmopolitan distribution of the genus may relate to this primary feeding strategy. INTRODUCTION