A truly gigantic pliosaur (Reptilia, Sauropterygia) from the Kimmeridge Clay Formation (Upper Jurassic, Kimmeridgian) of England

David M. Martill, Megan L. Jacobs, Roy E. Smith

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Four isolated cervical vertebrae from the Kimmeridge Clay Formation (Upper Jurassic, Kimmeridgian) of Abingdon, Oxfordshire, England are identified as from a pliosaurid plesiosaurian sauropterygian on account of their shortness relative to width and height, their near platycoelous nature and the location of tall rib facets on the centrum body. They are noteworthy for their size, with a maximum width of 269 mm, maximum height of 222 mm and maximum length of 103 mm. Simple scaling and comparisons with cervical vertebrae of Mid Jurassic pliosaurs Peloneustes and Liopleurodon, and the Early Cretaceous Stenorhynchosaurus and Sachiasaurus suggest a total body length of between ~ 9.8 m and 14.4 m for the Abingdon Kimmeridge Clay pliosaur. Likely the true length was towards the higher end of this range.

A genus and species cannot be confidently determined on the basis of the described material, but they likely belong to Pliosaurus sp. or a similar animal, for which a precise neck length is not known. We estimate a neck length of 0.77 m for Pliosaurus ?brachyspondylus based on the average cervical lengths provided for specimen CAMSM J.35991.
Original languageEnglish
JournalProceedings of the Geologists' Association
Early online date10 May 2023
Publication statusEarly online - 10 May 2023


  • Sauropterygia
  • Pliosauridae
  • Late Jurassic
  • Kimmeridgian
  • Giant-size
  • England

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