apato·​sau·​rus ə-ˌpa-tə-ˈsȯr-əs How to pronounce apatosaurus (audio)
variants or less commonly apatosaur
: any of a genus (Apatosaurus of the family Diplodocidae) of very large, herbivorous, sauropod dinosaurs that lived during the Late Jurassic period and reached a length of over 65 feet (20 meters) and a height of 12 feet (3.7 meters) and are thought to have attained a weight of up to 30 tons (27 metric tons)

Note: Apatosauruses were first identified as being of a separate genus (Brontosaurus) and continue to be commonly called brontosauruses or brontosaurs based on this earlier and now invalid classification.

Example Sentences

Recent Examples on the Web The Largest Life Over the years, biologists have identified over 250 distinct sauropod species, including several species from the famous apatosaurus and brachiosaurus genera. Sam Walters, Discover Magazine, 11 May 2023 The fossil record reveals that several types of sauropods, including the apatosaurus, buried their babies instead of brooding them, leaving them to emerge from their shells all on their own. Sam Walters, Discover Magazine, 21 Mar. 2023 Watch Brave on Disney+ The Good Dinosaur A young apatosaurus named Arlo befriends a human boy when he's swept away from his family in this heartwarming 2015 movie. Sydni Ellis, Peoplemag, 17 Mar. 2023 The fossil was found in the same Rocky Mountain region that has produced dinosaurs like apatosaurus, allosaurus and stegosaurus, according to the Utah DNR. Jordan Culver, USA TODAY, 22 May 2020 The resulting film is a sixth-grade sketchbook mash of dino-murder, cartoonish villains, and plot holes big enough for an apatosaurus to fit through. Sam Machkovech, Ars Technica, 22 June 2018 There were stegosauruses, apatosauruses, a T-rex, but the parasaurolophus, in all its weird glory, was always my favorite. Katherine Clover, The Cut, 15 Feb. 2018 Kids can also meet a baby apatosaurus, take an exciting spin in the Jurassic Jeeps and play in themed bounce houses, dig for fossils, do crafts, enjoy face-painting and more. Oc Disney Staff, Orange County Register, 1 Apr. 2017 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'apatosaurus.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


borrowed from New Latin, genus name, from Greek apátē "deceit" (perhaps of substratal origin) + New Latin -o- -o- + -saurus -saurus

Note: The genus name Apatosaurus was introduced by the American paleontologist Othniel Charles Marsh (1831-99) in "Notice of New Dinosaurian Reptiles from the Jurassic formation," American Journal of Science and Arts, 3rd series, vol. 14, no. 74 (December, 1877), pp. 514-16. As with other genera he named, Marsh gives no explanation of the taxon's components. Presumably it was inspired by the distinct chevron bones of Apatosaurus relative to those of other dinosaurs ("The chevron bones differ from those of most known Dinosaurs in having the superior articular ends of the rami not united, but separated from each other, as in the Mososauria with free hæmapophyses.").

First Known Use

1878, in the meaning defined above

Time Traveler
The first known use of apatosaurus was in 1878

Dictionary Entries Near apatosaurus

Cite this Entry

“Apatosaurus.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/apatosaurus. Accessed 7 Jun. 2023.

Kids Definition


apato·​sau·​rus ə-ˌpat-ə-ˈsȯr-əs How to pronounce apatosaurus (audio)
: any of several very large long-necked plant-eating dinosaurs

More from Merriam-Webster on apatosaurus

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