Largest known specimen of the genus Dakosaurus (Metriorhynchidae: Geosaurini) from the Kimmeridge Clay Formation (Late Jurassic) of England, and an overview of Dakosaurus specimens discovered from this formation (including reworked specimens from the Woburn Sands Formation)

Abstract

We report the largest known British specimen of the metriorhynchid crocodylomorph genus Dakosaurus discovered offshore from Chesil Beach, Dorset, England (Kimmeridge Clay Formation). This specimen is large toothed, which has extreme enamel spalling on the labial surface, enlarged carinae (‘carinal flanges’), carinal wear, macroziphodont denticles, and the crown retains much of its labiolingual width along most of its apicobasal length. This suite of morphologies is unique to Dakosaurus. All known Kimmeridge Clay Formation Dakosaurus specimens are isolated tooth crowns. A skull previously referred to Dakosaurus lacks all the cranial apomorphies of D. maximus and D. andiniensis, and cannot be referred to this genus. Furthermore, the vast majority of putative Dakosaurus tooth crowns from the ‘Potton Sands’ ( = Woburn Sands Formation) do indeed represent Dakosaurus (as well as two Plesiosuchus specimens), and they most likely originate from the Kimmeridge Clay Formation.

Keywords::

• Crocodylomorpha
• Dakosaurus
• England
• Kimmeridge Clay Formation
• Metriorhynchidae
• Woburn Sands Formation

Acknowledgements

The authors thank Steve Etches (Etches Collection, Kimmeridge, England) and Rainer Schoch (SMNS) for providing collections access. Lisa di Tomasso and Lisa Atalla (NHMUK) and Andrew Morrison (British Geological Survey) are thanked for checking historical information in their archives. The authors also thank Phil Hurst (NHMUK Image Resources) for specimen photography and Julian Hume (NHMUK) for digital image manipulation. The authors also thank Bernard O'Connor for discussions on the Potton Sands and two anonymous reviewers whose comments improved the quality of this paper.

Notes

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