di·​met·​ro·​don dī-ˈme-trə-ˌdän How to pronounce dimetrodon (audio)
plural dimetrodons
: an extinct, North American, primitive synapsid (genus Dimetrodon) of the early Permian comprising terrestrial carnivores of moderate size having both canine and shearing teeth and distinguished by a large dorsal crest resembling a sail supported by greatly elongated bony processes of the spinal column

Note: Dimetrodons are often mistaken for dinosaurs but were extinct more than 35 million years before dinosaurs appeared on earth.

Word History


borrowed from New Latin, genus name, from Greek di- di- + -metros "having the extent, size, or limit indicated" (adjective derivative of métron "measure") + -odōn "having teeth of the kind specified," adjective derivative of ódōn, ódous "tooth" — more at measure entry 1, tooth

Note: The taxon was introduced by the American paleontologist Edward Drinker Cope (1840-97) in "Description of Extinct Batrachia and Reptilia from the Permian formation of Texas (Read before the American Philosophical Society, April 5, 1878)," Paleontological Bulletin, no. 29 (1878), pp. 512-14 (also published with the same title and pagination in Proceedings of the American Philosophical Society, vol. 17, June, 1877 to June, 1878). The name, meaning approximately "having teeth of two sizes," presumably refers to the discrepancy in tooth size ("The anterior two teeth of the maxillary bone are larger than those that follow, the anterior exceeding even the first incisor").

First Known Use

1885, in the meaning defined above

Time Traveler
The first known use of dimetrodon was in 1885

Dictionary Entries Near dimetrodon

Cite this Entry

“Dimetrodon.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/dimetrodon. Accessed 29 Mar. 2023.

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