Etymology
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mastodon (n.)

"large, extinct, forest-dwelling elephant-like mammal of North and Central America," 1813, from Modern Latin genus name Mastodon (1806), coined by French naturalist Georges Léopole Chrétien Frédéric Dagobert, Baron Cuvier (1769-1832) from Greek mastos "breast" (see masto-) + -odon "tooth" (from PIE root *dent- "tooth"); so called from the nipple-like projections on the crowns of the mammal's fossil molars. They died out about 10,500 years ago, probably hunted to extinction by humans. Their bones had been dug up in America since 1705, but at first they were confused with those of the mammoth. Related: Mastodontic.

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iguanodon (n.)
dinosaur name, 1825, hybrid from iguana + Latinized stem of Greek odonys "tooth" (on model of mastodon). So called because the fossil teeth and bones were thought to resemble (except in size) those of the tropical lizard.
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