1. any fishlike marine reptile of the extinct order Ichthyosauria, ranging from 4 to 40 feet (1.2 to 12 meters) in length and having a round, tapering body, a large head, four paddlelike flippers, and a vertical caudal fin.

Origin of ichthyosaur

First recorded in 1820–30; see origin at ichthyosaurus
Related formsich·thy·o·sau·ri·an, adjective, nounich·thy·o·sau·roid, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for ichthyosaur

Historical Examples of ichthyosaur

  • The Ichthyosaur of the Jurassic is a remarkably fish-like animal.

  • The Ichthyosaur came of the reptile group which we have called the Diapsids.

  • It is supposed to have lived in shallow seas and estuaries, and to have breathed air like the Ichthyosaur, and our modern cetacea.

  • In the popular mind, perhaps, the Ichthyosaur and Plesiosaur are the typical representatives of that extinct race.

  • Compared with the Ichthyosaur, it was what the giraffe is to the rhinoceros, or the swan to the porpoise.

British Dictionary definitions for ichthyosaur


ichthyosaurus (ˌɪkθɪəˈsɔːrəs)

noun plural -saurs, -sauruses or -sauri (-ˈsɔːraɪ)
  1. any extinct marine Mesozoic reptile of the order Ichthyosauria, which had a porpoise-like body with dorsal and tail fins and paddle-like limbsSee also plesiosaur
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for ichthyosaur



extinct reptile, 1830, Modern Latin, from Greek ikhthys "fish" + sauros "lizard" (see -saurus).

Online Etymology Dictionary, © 2010 Douglas Harper

ichthyosaur in Science


  1. Any of various extinct sea reptiles of the genus Ichthyosaurus and related genera, that had a medium-sized to large dolphin-like body with a dorsal fin, four flippers, and a large, crescent-shaped tail. The head had a long beak with sharp teeth, large eyes and earbones, and nostrils near the eyes on top of the skull. Ichthyosaurs were most common and diverse in the Triassic and Jurassic Periods and died out well before the end of the Cretaceous.
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