Pliosaurus

Abstract: The Late Jurassic genus Pliosaurus was erected by Owen in 1841a Since then numerous isolated bones and more complete skeletons have been referred to various species within the genus, many based on non-diagnostic material which has led to many uncertainties regarding the taxonomic status of Pliosaurus Here, the species of Pliosaurus, their type and referred material are re-evaluated Lack of distinctive type material demands selection of a neotype for P macromerus (Philips, 1871) Lydekker, 1889a and a new neotype for P brachyspondylus (Owen, 1839) Eichwald, 1868 Four species are recognised based on cranial tooth counts, cervical centrum morphology, retroarticular morphology, and relative propodial length Three previously accepted named taxa are here considered invalid This study is also the first to collectively illustrate an accurate stratigraphic provenance to, and what material is available from the main specimens referred to Pliosaurus The results of this work form a foundation on which to build a more solid understanding of the diversity of this genus

Abstract: A new and unusual pliosaurid from the Peterborough Member, Oxford Clay Formation (Callovian, Jurassic) of Cambridgeshire, UK, exhibits a type of pachyostosis and bone thickening of the rib cage and vertebrae. Pachycostasaurus dawni gen. et sp. nov. was most probably a benthic feeding carnivore with a generalist diet that included fish and invertebrates, and was a slow swimming underwater flyer with ventrally placed ballasting of the skeleton to resist roll. The apparent rarity of this pliosaur may indicate that it is allochthonous in the Oxford Clay biota. From a palaeoecological viewpoint, the find is significant for two reasons. Firstly, as an air breathing animal that is thought to have fed on benthos or nektobenthos, Pachycostasaurus may have been important in transferring resources from the benthic food web to the surface food web. In a more general sense, the new find provides further insights into the possible trophic structure of aquatic animal communities during deposition of the Oxford Clay.

Abstract: ‘Tarlo's Contention’, that a mandible possessing five to six large caniniform teeth characterizes Pliosaurus macromerus is explored and shown to rest on the assumption that only two morphologies of pliosaur mandibular symphysis exist in the Kimmeridge Clay Formation. A new taxon, Pliosaurus portentificus sp. nov., is described based on a third mandibular symphysial morphology from the Kimmeridge Clay near Ely, Cambridgeshire, UK. This specimen invalidates ‘Tarlo's Contention’, which was the basis for reassigning Stretosaurus macromerus (formerly Pliosaurus macromerus ) to the genus Liopleurodon . All material currently assigned to Liopleurodon macromerus should revert to the original combination of Pliosaurus macromerus Phillips, 1871 .

Abstract: The Blue Circle Industries pic Westbury Works is a major marine vertebrate-bearing exposure in the Lower Kimmeridge Clay of Wiltshire. The quarry faces have yielded important chelonian, ichthyosaurian, crocodilian and plesiosaurian remains. The most recent discovery is a large pliosaurian skeleton found during the summer of 1994. The partial skeleton, provisionally identified as Pliosaurus , consists of a skull and mandible (approximately 1.8 m in length), with associated disarticulated postcrania enclosed within large carbonate concretions. The skeleton is associated with abundant fossil wood and shell debris, indicating a possible period of turbulent current activity in the vicinity of the carcass prior to burial.