ple·​si·​o·​saur ˈplē-sē-ə-ˌsȯr How to pronounce plesiosaur (audio)
: any of an order or suborder (Plesiosauria) of large carnivorous marine reptiles of the Mesozoic with dorsoventrally flattened bodies and limbs modified into flippers

Example Sentences

Recent Examples on the Web In 2006, facing 70-mile-per-hour winds, a U.S.-Argentinian research team recovered one of the most complete skeletons of a plesiosaur, a prehistoric marine reptile that lived in the Southern Ocean. Discover Magazine, 24 Jan. 2018 The remains of the 6-meter (19 feet) tall juvenile long-necked plesiosaur, also known as an elasmosaur, were found by a trio of amateur fossil hunters on a cattle station in the western Queensland outback in August. Kathleen Magramo, CNN, 7 Dec. 2022 But the possibility of a modern-day plesiosaur being seen in rivers wasn’t plausible. Joshua Hawkins, BGR, 28 July 2022 Could the Loch Ness monster actually have been a plesiosaur? Saleen Martin, USA TODAY, 2 Aug. 2022 Another part was that Nessie most closely resembles the plesiosaur. Joshua Hawkins, BGR, 28 July 2022 The plesiosaur — an aquatic dinosaur once thought to exclusively reside in saltwater — is now believed to have spent much of its time in freshwater, according to a new study. Tori B. Powell, CBS News, 13 Aug. 2022 Locals in Morocco found fossils belonging to the plesiosaur in a 100-million-year-old freshwater river system. Saleen Martin, USA TODAY, 2 Aug. 2022 No plesiosaur has lived for many millions of years. Caroline Delbert, Popular Mechanics, 29 July 2022 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'plesiosaur.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Word History


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

First Known Use

1839, in the meaning defined above

Time Traveler
The first known use of plesiosaur was in 1839

Dictionary Entries Near plesiosaur

Cite this Entry

“Plesiosaur.” Dictionary, Merriam-Webster, Accessed 5 Feb. 2023.

Kids Definition


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

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