1. Large marine reptiles that lived during the Mesozoic Era, characterized by long necks, four flippers, and streamlined bodies.
Usage: plural of plesiosaur; paleontology term; extinct animals

Examples

• Plesiosaurs were among the most successful marine predators of the Mesozoic Era.
• Scientists have discovered numerous plesiosaur fossils in marine rock formations.
• The long necks of plesiosaurs allowed them to hunt fish and other prey in shallow waters.
• Unlike dinosaurs, plesiosaurs were adapted for life in the ocean.
• Many plesiosaurs grew to lengths of 30 feet or more.