A revision of Temnodontosaurus crassimanus (Reptilia: Ichthyosauria) from the Lower Jurassic (Toarcian) of Whitby, Yorkshire, UK

ABSTRACT

While the holotype of Temnodontosaurus crassimanus still remains on display at the Yorkshire Museum, it has remained largely understudied and the validity of the species has long been questioned. Through re-examination, this study highlights several morphological features of the postcranial skeleton and determines that T. crassimanus is a valid species of the genus and includes several distinct characters that can be used to distinguish it from T. trigonodon, to which it was once assigned. These include a large, robust humerus that is proximodistally longer than the scapula (scapula length vs humerus length ratio: ~0.68); forefins which are significantly longer but less than twice the length of the hindfin (forefin length vs hindfin length ratio: ~1.51); the relative size of the forefins compared with the total body length; along with several other characters that may prove to be unique, such as humerus distal width almost equal to humerus length; presence of notching in at least five leading edge elements of both the fore- and hindfins; and anteroposteriorly wider fore- and hindfins compared with T. trigonodon. Additional specimens, previously tentatively assigned to T. crassimanus, were located and examined, but none could confidently be assigned to the species.

KEYWORDS:

• Temnodontosaurus
• Temnodontosaurus trigonodon
• Lower Jurassic
• Whitby
• Yorkshire
• Holzmaden

Acknowledgments

The authors would like to acknowledge the help of Sarah King and Stuart Ogilvy of the Yorkshire Museum, York, for kindly making this specimen available for study. Further thanks is extended to the following museums (and persons) for allowing access to examine additional specimens and/or for providing relevant specimen information and photographs included within this research; they include: WHITM (Roger Osborne); SMNS (Erin Maxwell); MANCH (Kate Sherburn, David Gelsthorpe); and NHMUK (Sandra Chapman). Initial research of this project formed a postgraduate (MPhil) dissertation by EJS in 2019, supervised by DRL and John Nudds. We would like to extend thanks to Mark Evans for his feedback on the original thesis, in addition to John Nudds as co-supervisor of the project and for his assistance and advice through each stage of the MPhil process, which has been invaluable. Further thanks are due to Sven Sachs who provided a critical review of the manuscript, which greatly improved it.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed here.