The first relatively complete exoccipital-opisthotic from the braincase of the Callovian pliosaur, Liopleurodon

A newly recognized left exoccipital-opisthotic of a Callovian pliosaur, derived from the Peterborough or lower Stewarby Members of the Oxford Clay Formation of Peterborough, is described and figured. This isolated bone is tentatively identified as belonging to an ‘adult’ individual of Liopleurodon ferox that is inferred to have had a skull length of 1.26 metres and an overall body length of 6.39 metres

Evolutionary pathways toward gigantism in sharks and rays

Through elasmobranch (sharks and rays) evolutionary history, gigantism evolved multiple times in phylogenetically distant species, some of which are now extinct. Interestingly, the world's largest elasmobranchs display two specializations found never to overlap: filter feeding and mesothermy. The contrasting lifestyles of elasmobranch giants provide an ideal case study to elucidate the evolutionary pathways leading to gigantism in the oceans. Here, we applied a phylogenetic approach to a global dataset of 459 taxa to study the evolution of elasmobranch gigantism. We found that filter feeders and mesotherms deviate from general relationships between trophic level and body size, and exhibit significantly larger sizes than ectothermic‐macropredators. We confirm that filter feeding arose multiple times during the Paleogene, and suggest the possibility of a single origin of mesothermy in the Cretaceous. Together, our results elucidate two main evolutionary pathways that enable gigantism: mesothermic and filter feeding. These pathways were followed by ancestrally large clades and facilitated extreme sizes through specializations for enhancing prey intake. Although a negligible percentage of ectothermic‐macropredators reach gigantic sizes, these species lack such specializations and are correspondingly constrained to the lower limits of gigantism. Importantly, the very adaptive strategies that enabled the evolution of the largest sharks can also confer high extinction susceptibility

The occurrence of the Middle Jurassic pachycormid fish Leedsichthys

A review of the occurrences of the Middle Jurassic pachycormid fish Leedsichthys is presented, including a new French locality. The variety of past misidentifications of these remains is noted, and the bones reinterpreted according to information derived from the broader hypodigm of material available for study. Trace fossils from the Lower Callovian outside Basel in Switzerland are assessed with regard to Leedsichthys, in addition to a review of relevant body fossil material from France, Germany and Chile