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

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

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

Finding a plesiosaur fossil is rare compared to other fossilized marine reptiles from that time, like ichthyosaurs. —Monica Cull, Discover Magazine, 31 Mar. 2025

For fossil plesiosaurs around 183 million years ago, the answer was a bit of both. —Sam Walters, Discover Magazine, 10 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