Two ichthyosaurs become one

by Lucas Joel
Friday, June 16, 2017

Dean Lomax examines an ichthyosaur fossil on display at the Bristol Museum and Art Gallery in England. Credit: Nigel Larkin.

While dinosaurs ruled on land in the Mesozoic, dolphin-like marine reptiles called ichthyosaurs roamed the oceans. Paleontologists first described the genus in 1821 based on remains discovered in England, naming the first species Ichthyosaurus communis. The description of a second species, I. intermedius, followed in 1822. Although these two species were the earliest-known ichthyosaurs, they are also some of the most poorly understood, as their initial descriptions were based on limited remains.

“To complicate matters further, the original specimen of I. communis is lost and was never illustrated. Similarly, the original specimen of I. intermedius is also lost, but an illustration does exist,” said Dean Lomax, a paleontologist at the University of Manchester in England and co-author of a new study in the Journal of Systematic Palaeontology that concludes the two species are one, in a statement.

In the new study, Lomax and lead author Judy Massare, a paleontologist at the State University of New York, College at Brockport, examined other remains of I. communis and I. intermedius. The species were previously distinguished based on tooth morphology, which has been shown to be unreliable as a diagnostic trait. The newly conjoined species, called I. communis, is now defined by skeletal features like a triangular, symmetric upper jawbone and a broad, triradiate lacrimal (a bone that forms part of the eye socket).

© 2008-2021. All rights reserved. Any copying, redistribution or retransmission of any of the contents of this service without the expressed written permission of the American Geosciences Institute is expressly prohibited. Click here for all copyright requests.