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

Dinosaur fans know that late Cretaceous-era waters were ruled by sharp-toothed sharks and sea reptiles known as mosasaurs and plesiosaurs. —CBS News, 24 Apr. 2026

These octopuses shared their environment with mosasaurs and plesiosaurs, marine reptiles that grew up to 50 feet, and sharks comparable in size to modern great whites. —Ryan Brennan, Miami Herald, 24 Apr. 2026

These octopuses shared the oceans with giant marine reptiles like mosasaurs and plesiosaurs — some reaching up to 50 feet long — as well as sharks comparable to modern great whites. —Ryan Brennan april 24, Fort Worth Star-Telegram, 24 Apr. 2026

These massive mollusks may even have eaten large aquatic reptiles like mosasaurs and plesiosaurs, which were themselves believed to be among the main marine predators of the time. —Adam England, PEOPLE, 24 Apr. 2026

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

• albacore
• alongshore
• antiwar
• anymore
• blastopore
• carnivore
• commodore
• dinosaur
• evermore
• furthermore
• guarantor
• herbivore

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