Ichthyosaurs of the British Middle and Upper Jurassic Part 1, Ophthalmosaurus

ABSTRACT The ichthyosaur material of the British Middle and Upper Jurassic referable to Ophthalmosaurus icenicus (Ichthyosauria: Ophthalmosauridae) is revisited and re-described; this is the most completely known post-Liassic British ichthyosaur. Much of this material derives from the Callovian Oxford Clay Formation, particularly from the Peterborough Area of Cambridgeshire, UK, deposited in the Leeds Collections. Pre-Callovian ichthyosaur remains are infrequent, incomplete, and non-diagnostic. Material referred to Ophthalmosaurus icenicus shows high variability in the extent of ossification. Based on examination of the type and referred material, Ophthalmosaurus monocharactus and Ophthalmosaurus pleydelli are rejected as junior subjective synonyms of Ophthalmosaurus icenicus due to a lack of diagnostic characters and pathology of specimens. Ichthyosaurus megalodeirus is rejected as a nomen nudum and the type material is referred to Ophthalmosaurus icenicus. Ophthalmosaurus icenicus is considered a separate species from Ophthalmosaurus natans based on several autapomorphies, but requires re-evaluation of the material.