Taxonomic revision of the family Squalodontidae (Cetacea, Odontoceti): emptying the wastebasket of fragmentary holotypes

Abstract The Squalodontidae are one of the most historic families within the Cetacea, given that Squalodon was first named in 1840. Since Squalodon' s initial description, workers in the 1800s were eager to assign heterodont cetacean teeth to this family; as a result, it became a wastebasket with many species based on fragmentary remains. Taxa represented by well‐preserved specimens demonstrate that the Squalodontidae possess a mixture of ancestral and derived traits: they exhibit polydonty as most modern odontocetes do, but their teeth are still differentiated into incisor, canine and molariform types. Despite their position as a transitional form, the Squalodontidae have been neglected in the scientific literature and much of this is due to their poorly resolved taxonomy. While revisional work has been done for the North American record, the European record has remained a wastebasket. We assess here the taxonomic status of the 22 species in two squalodontid genera recorded from Europe spanning from the Chattian to the Serravallian. Both species of Eosqualodon bear diagnostic name‐bearing specimens. However, of the 20 species of Squalodon , only six bear diagnostic types, and of those, one is a junior synonym. Our literature review of historic papers shows that the other 14 species of Squalodon have non‐diagnostic name‐bearing types, are synonymous with other species of Squalodon , or never had a specimen associated with the name. We also call into question the assertion that the Squalodontidae persist into the Serravallian, given that the youngest family‐diagnostic specimens are found in units straddling the Langhian–Serravallian boundary.