1. a large marine reptile of the Mesozoic era with a long neck, four flippers, and a small head
Usage: paleontology; often used in plural as 'elasmosaurs'

Examples

• The elasmosaur was one of the most distinctive marine reptiles of the Cretaceous period.
• Fossils of elasmosaurs have been found on every continent.
• An elasmosaur could reach lengths of up to 46 feet.
• The long neck of an elasmosaur allowed it to hunt fish in shallow waters.
• Scientists study elasmosaur remains to understand ancient ocean ecosystems.