mastodon Look up mastodon at Dictionary.com
1813, from Mod.L. genus name Mastodon (1806), coined by Fr. naturalist Georges Léopole Chrétien Frédéric Dagobert, Baron Cuvier (1769-1832) from Gk. mastos "breast" + odont- "tooth," so called from the nipple-like projections on the crowns of the extinct mammal's fossil molars.
iguana Look up iguana at Dictionary.com
1555, from Sp., from Arawakan 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]
Dinosaur name Iguanodon is 1830, from iguana + stem of Gk. odonys "tooth," on model of mastodon; so called because the fossil teeth and bones were thought to resemble those of the lizard.