Description of new Kimmerosaurus langhami (Cryptoclididae, Plesiosauria) material recovered from the Kimmeridge Clay Formation, Dorset, U.K.

A new specimen of the cryptoclidid plesiosauroid Kimmerosaurus langhami (EC K2134) is described from the Upper Jurassic Kimmeridge Clay Formation, Kimmeridge Bay, Dorset, U.K. We provide new insights into the cranial morphology of this taxon, and significantly, we report the discovery of the first cryptoclidid hyoid, a useful comparative element for future studies. Comprehensive investigations into the anatomy and paleobiology of Kimmerosaurus langhami have been hampered by the scarcity of relevant fossil material. The previous cranial reconstruction of Kimmerosaurus was based on incomplete skull material consisting of part of the skull roof, brain case, dentary, teeth, and vertebrae. Using computed tomography (CT) scanning, we provide high-resolution 3D images of the new material, adding the rostrum, palate, and revised tooth count to the reconstruction. In addition, this new material provides significant insights into the cranial and anterior cervical morphology of K. langhami. Phylogenetic results support the referral of the specimen, placing EC K2134 in a polytomy with the North American taxon Tatenectes laramiensis and known material of K. langhami. This study highlights the use of computed tomography for description of Kimmeridge Clay fossil material.