# plesiosaur

> English word · Noun · IPA /ˈpliːsiəsɔːɹ/

## Definitions
1. Any of the order †Plesiosauria of extinct marine reptiles, from the Jurassic and Cretaceous periods.

## Etymology
Backformation of translingual Plesiosaurus, named by William Conybeare and Henry De la Beche in 1824 because plesiosaurs were more like a normal reptile than Ichthyosaurus, which had been found in the same rock strata a few years earlier. Surface derivation, plesio- + -saur.

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/plesiosaur