This bone is a humerus, the main bone that supported the upper front paddle. Its shape is typical for ichthyosaurs that lived at a particular time in the Upper Jurassic period.
This fossil is a holotype and as such defines the species Ophthalmosaurus pleydelli, named after J C Mansel-Pleydell who collected and donated a considerable amount of Dorset County Museum’s fossil collection. Opthalmosaurs are a variety of ichthyosaur with massive eyes. They first appeared in the Upper Jurassic Oxford and Kimmeridge Clay rocks which both formed in muddy seas where presumably visibility was poor.
Find out more on the reptiles pages.