Cranial anatomy, taxonomic implications and palaeopathology of an Upper Jurassic Pliosaur (Reptilia: Sauropterygia) from Westbury, Wiltshire, UK

Abstract

Complete skulls of giant marine reptiles of the Late Jurassic are rare, and so the discovery of the 1.8-mlong skull of a pliosaur from the Kimmeridge Clay Formation (Kimmeridgian) of Westbury, Wiltshire, UK, is an important find. The specimen shows most of the cranial and mandibular anatomy, as well as a series of pathological conditions. It was previously referred to Pliosaurus brachyspondylus, but it can be referred reliably only to the genus Pliosaurus, because species within the genus are currently in need of review. The new specimen, together with another from the same locality, also referred to P. brachyspondylus, will be crucial in that systematic revision, and it is likely that the genus Pliosaurus will be found to include several genera. The two Westbury Pliosaurus specimens share many features, including the form of the teeth, but marked differences in the snout and parietal crest suggest sexual dimorphism; the present specimen is probably female. The large size of the animal, the extent of sutural fusion and the pathologies suggest this is an ageing individual. An erosive arthrotic condition of the articular glenoids led to prolonged jaw misalignment, generating a suite of associated bone and dental pathologies. Further damage to the jaw joint may have been the cause of death.

A Giant Pliosaurid Skull from the Late Jurassic of England

“…Although ‘ Pleiosaurus ’ is the correct original spelling (in the sense of Article 32 of the ICZN), as far as we know, no authors have used this spelling since Phillips in 1871 [35]. Instead, ‘ Pliosaurus ’, is in prevailing usage (e.g., [17], [34], [42]–[43], [54]–[55]), and should be preserved (Article 33.3.1 of the ICZN).…”

“…Many are isolated bones and teeth or skeletal fragments (e.g., [31], [43], [50]–[51]). However, others comprise more complete cranial remains, some with associated postcrania [15], [42], [52]–[55], and partial postcranial skeletons [56]–[57]. Although many species of Kimmeridge Clay Formation pliosaurid have been erected, only three have recently been considered valid [17], [34], [54]: Pliosaurus brachydeirus , P .…”

“…These vertebrae were considered undiagnostic in the most recent taxonomic appraisal of Pliosaurus [34]. In consequence, even the more complete and informative pliosaurid skulls and skeletons are in taxonomic limbo [34], [42], [51], [54]–[55]. Thus, substantial work remains to understand pliosaurid diversity and evolution in the Kimmeridge Clay Formation.…”

The Cranial Osteology and Feeding Ecology of the Metriorhynchid Crocodylomorph Genera Dakosaurus and Plesiosuchus from the Late Jurassic of Europe

“…However, the taxonomy of these species is still highly uncertain [119], [120]. Confusion surrounds taxonomy at both the generic and specific levels, and about the referral of specimens to species with no overlapping elements.…”

Plasticity and Convergence in the Evolution of Short-Necked Plesiosaurs

“…,60]), crown shape (crown height divided by the basal diameter of the crown, largest tooth), relative skull size (mandible length divided by trunk length), relative neck length (neck length divided by trunk length), homogeneity of flipper sizes (humerus proximodistal length divided by femur proximodistal length) and flipper size (mandible length divided by femur length). In addition to our own measurements, we used the following references for pliosaurids: [1,6,13,15,16,22,23,26,27,30,31,[61][62][63][64][65][66] and the following references for polycotylids [7,28,29,41,45,47,67,68] (see Data S3 and Data S4 for more information). We then applied a 50% completeness threshold to remove the influence of highly incomplete taxa.…”