COMPARISON AND ANALYSIS OF ICHTHYOSAURUS BREVICEPS AND ICHTHYOSAURUS COMMUNIS TO NEW THREE-DIMENSIONAL JURASSIC-AGED ICHTHYOSAURUS SKULL FOSSIL, FOUND ON THE DORSET COAST, UK

In this study, a three-dimensional Ichthyosaur skull fossil was analyzed to determine whether it belonged to the relatively common Ichthyosaurus communis species or the rare Ichthyosaurus breviceps species. The three-dimensional preservation of the fossil is unique because deformation occurred in the dorsal-ventral direction, preserving the detailed anatomy of the skull roof. Measurements of the skull such as the length of the snout and the diameter of the orbit were taken for species comparison. The Ichthyosaur specimen matches closely to I. breviceps because it has a shorter snout and larger eyes, which are diagnostic traits of the species. The length of the snout to length of the jaw has a ratio of 0.449 on the study specimen compared to a ratio of 0.57-0.69 for I. communis and <0.57 for I. breviceps. The diameter of the orbit to the length of the jaw has a ratio of 0.327 for the study specimen compared to a ratio of 0.20-0.28 for I. communis and >0.25 for I. breviceps. Diagenetic crushing of the skull during fossilization has restricted the accuracy of certain measurements, limiting the ability to determine the precise identification of the species. Bone texture was used to determine the maturity level of the specimen. The nasal and frontal bones contain long-grained texture indicative of a juvenile. However, a comprehensive study of Ichthyosaur bone texture is needed to determine the ontogenetic significance of these data.