Learn how to say Plesiosaurs correctly in English with this tutorial pronunciation video.
Oxford dictionary definition of the word plesiosaur:
a large fossil marine reptile of the Mesozoic era, with a broad flat body, large paddle-like limbs, and typically a long flexible neck and small head.
Infraorder Plesiosauria, superorder Sauropterygia: several families, including Plesiosauridae
mid 19th century: from modern Latin Plesiosaurus, from Greek plēsios ‘near’ + sauros ‘lizard’