...A. R. I. CRUICKSHANK; D. M. MARTILL; L. F. NOÈ 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...

.... Arambourg ( 1952 ) only shortly described the specimens and provided a brief diagnosis: ‘aquatic lacertilian with shortened vertebrae and centra triangular, short, almost as wide as long, and remarkable by their general pachyostosis’ (translated from French). It is worth pointing out that the osteoderms...

... relative size and density, has been considered an important indicator of the ability of a marine mammal to localize sound transmitted in water, yet petrosal size (pachyostosis) and density (osteosclerosis) have not previously been quantified independent of each other. We examine the new fossils...

... on the anterior part of the skull, previously described as external nares, are probably internal nares. Important features not noted previously include accessory articulations on all presacral vertebrae, pachyostosis of dorsal vertebrae and ribs, and the presence of two pygal vertebrae. Phylogenetic analysis...

... are all broken off (embedded in the counterpart) and their height cannot be determined. However, they were wide transversely as a correlate of pachyostosis and extended anteroposteriorly along the entire length of the neural arch. Ribs are associated with all vertebrae but are only exposed proximally...

..., as is evident from Haas' (1979 , 1980a , 1980b) comments on the relationships of Pachyrhachis and Estesius . Pachyrhachis was first classified as a symoliophid [with which the fossil shares mid-trunk pachyostosis and the general outline of the trunk vertebrae ( Nopcsa, 1925 )], but the symoliophids...

... spines appear to be low, but mostly show an abraded dorsal margin. Pachyostosis is distinct in the prezygapophyses and postzygapophyses, a character known to occur in the genus Lariosaurus ( Rieppel 1998 a ). The average dorsal vertebra is 16–17 mm long (measured along the midline of the neural arch...

... by pachyostosis. Simoliophis rochebrunei S auvage , 1880 is estimated to about 1.5 m long. It has been originally very briefly described and no revision has been published. It is known from several localities of early and mid Cenomanian age of western France, as well as from the middle Cenomanian...

... facet is located on the preserved anterior end of the left process. Pachyostosis is expressed as low neural canal, robust metapophyses and postzygapophyses, the lateral expansion of neural arch and the base of the neural spine. Figure 5 Vertebra TA of Basilotritus uheni n. gen. n. sp., NMNH-P...

... nomenclature of the Oxford Clay (Jurassic) . Proceedings of the Geologists’ Association 103 , 343 – 5 . Cruickshank , A. R. I. , Martill , D. M. & Noe ‘ , L. F. 1996 . A pliosaur (Reptilia, Sauropterygia) exhibiting pachyostosis from the Middle Jurassic of England . Journal...

... pachyostosis from the Middle Jurassic of England . Journal of the Geological Society (London) 153 , 873 –9. Doyle P. 1987 . Lower Jurassic–Lower Cretaceous belemnite biogeography and the development of the Mesozoic...

... and lateral flattening of the tail ( Carroll 1985 ). At the microanatomical level, the presence of spongy tissue in the center of the medullary region of long limb bones, as in cetaceans, or of massive pachyostosis, as in mesosaurs ( Ricqlès 1974a ), placodonts ( Buffrénil and Mazin 1992 ), and sirenians...

... pachyostosis (Gingerich et al . 1995 ; Zalmout, Ul-Haq & Gingerich, 2003 ). The cross-sections are similar to those of Prototherium solei from Catalonia (Pilleri, Biosca & Vía, 1989 , fig. 4a–c), Halitherium taulannense from Provence (undescribed material of Sagne, 2001 ), and an indeterminate...

... but thin zygosphene which is anteriorly incomplete. The aforementioned vertebrae and others do not show an evident pachyostosis in the zygapophyses or transverse processes. A fine preparation of WIGM SPC V 1009 indicates that the zygosphene–zygantrum articulation is also...

... S2 in the online Supplementary Material available at http://journals.cambridge.org/geo ): the parietal skull table weakly constricted [19 (1)], the pachyostosis of the dorsal ribs absent [72 (0)] and the bone in dermatocranium distinctly sculptured [138(0)]. Among the seven...

..., the humerus of D. delphis was drawn at a smaller scale Among aquatic tetrapods, two main microstructural organizations reflect aquatic adaptations. Taxa that live in shallow water display pachyostosis or an increase in compactness ( Laurin et al., 2004 ), whereas species that live in deep water tend...

... of Sedimentary Petrology , v. 42 , p. 227 – 229 . Street H.P. O'Keefe F.R. 2010 , Evidence of pachyostosis in the cryptocleidoid plesiosaur Tatenectes laramiensis from the Sundance Formation...

... into a broad mediolateral curvature, which is part of the semicircular canals. The vertebrae of Askeptosaurus are amphicoelous and there is no sign of pachyostosis. Intercentra could not be identified, but they may have been present as cartilaginous elements. Askeptosaurus possessed at least 38...

... in mesosaurs, suggesting that pachyostosis is a result of neoteny (de Ricqlès, 1974). Pachyostotic ribs are also correlated with a delay in the ossification in limb bones, carpus, and tarsus of aquatic organisms after limbs are freed from support of body weight ( Romer, 1956 ). Delay in the fusion...

... for Togocetus traversei , all from the middle part of the thorax. These are curved and slender like those of other early Protocetidae, and lack both pachyostosis and osteosclerosis. The most complete is KPG-M 143 ( Fig. 10 .1), 16 cm long, which preserves the body of a smoothly curving right rib from the base...