iguanodon n.

large lizard of the American tropics, 1550s, from Spanish, from Arawakan (West Indies) iguana, iwana, the local name for the lizard.

Foure footed beastes ... named Iuannas, muche lyke vnto Crocodiles, of eyght foote length, of moste pleasaunte taste. [Richard Eden, "Decades of the New World," 1555]

"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.