plesiosaur

noun

ple·​si·​o·​saur ˈplē-sē-ə-ˌsȯr 

-zē-

: any of an order or suborder (Plesiosauria) of large carnivorous marine reptiles of the Mesozoic with dorsoventrally flattened bodies and limbs modified into flippers

Examples of plesiosaur in a Sentence

Recent Examples on the Web

Fossils of plesiosaurs have been dated back to the Triassic period about 250 million years ago into the Cretaceous period, before dinosaurs vanished about 65 million years ago, according to Britannica. —Mike Snider, USA Today, 6 Aug. 2025

Mosasaurs, plesiosaurs, and sharks diversified and expanded. —Paul Smaglik, Discover Magazine, 2 May 2025

Editor's note: This story has been updated to reflect that the plesiosaur is considered a successful marine predatory ancient species. —Julia Jacobo, ABC News, 18 Feb. 2025

Everyone's favorite candidate for the identity of the Loch Ness monster, the plesiosaurs were a group of prehistoric marine reptiles that lived in oceans throughout the world between 203 and 66 million years ago. —Ben Coxworth, New Atlas, 7 Feb. 2025

Word History

Etymology

ultimately from Greek plēsios close (akin to Greek pelas near) + sauros lizard

First Known Use

1839, in the meaning defined above

Rhymes for plesiosaur

• conquistador
• forevermore
• hereinbefore
• kinetochore
• kwashiorkor
• abhor
• abor
• adore
• afore
• ardour
• ashore
• backdoor

Kids Definition

plesiosaur

noun

ple·​sio·​saur

ˈplē-sē-ə-ˌsȯ(ə)r,

-zē-

: any of a group of large Mesozoic marine reptiles with flattened bodies and limbs changed into paddles