: 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.

Examples of apatosaurus in a Sentence

Recent Examples on the Web
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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

Word History

Etymology

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 6 Jan. 2025.

Kids Definition

: any of several very large long-necked plant-eating dinosaurs

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