The Westerschelde Estuary in The Netherlands is well known for its rich yield of vertebrate fossils. In a recent trawling campaign aimed at sampling an assemblage of late Miocene marine vertebrates, over 5,000 specimens were retrieved, all currently stored in the collections of the Natuurhistorisch Museum Rotterdam. One of these is a well-preserved fragment of a dermochelyid carapace. The Westerschelde specimen is an interesting addition to the scant hypodigm of dermochelyids from the Miocene of the North Sea Basin. The carapace fragment is described and assigned to Psephophorus polygonus von Meyer, 1847. The secondary marks present on the fragment are suggestive of predation or scavenging. Furthermore, based on the physical traits of the Westerschelde specimen and a reexamination of specimens of P. polygonus, inclusive of the neotype held at the Naturhistorisches Museum Wien (Vienna, Austria), we argue that several previously assigned characteristics cannot be used as discriminative taxonomic properties amongst dermochelyids in general and of P. polygonus in particular. An improved cladistic analysis of dermochelyids is performed on the basis of previously defined and novel taxonomic characters. Our results indicate that Psephophorus calvertensis Palmer, 1909 is a junior synonym of P. polygonus. Hence, a new diagnosis of Psephophorus polygonus is proposed. The synonymy of P. calvertensis with P. polygonus also means that the latter had a cosmopolitan distribution, similar to the extant species Dermochelys coriacea (Vandelli, 1761).

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Cainozoic research

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Werkgroep voor Tertiaire en Kwartaire Geologie

Marit E. Peters, Mark E.J. Bosselaers, Klaas Post, & Jelle W.F. Reumer. (2019). A Miocene leatherback turtle from the Westerschelde (The Netherlands) with possible cetacean bite marks: identification, taphonomy and cladistics. Cainozoic research, 19(2), 121–133.