RECOGNISING COMPOSITE SPECIMENS OF JURASSIC ICHTHYOSAURS IN HISTORICAL COLLECTIONS

Composite specimens have been a problem in palaeontology since its beginning. Numerous composite specimens exist in museum collections assembled in the 19th century in the UK. Features of the ichthyosaurian vertebral column are often overlooked, but centrum morphology can be used to evaluate the authenticity of a specimen. In particular, two landmarks are useful for assessing authenticity in many derived Jurassic ichthyosaurs: (1) the transition from two articular processes to one on the centrum, which often occurs in the pelvic region, and (2) the presence of wedge-shaped centra at the tail bend. We apply these criteria to a specimen of Ichthyosaurus to show that more than half of the seemingly articulated vertebral column was added using centra from perhaps five other individuals.