An iguana was a reptilian animal native to Earth. Iguanas could grow up to almost two meters long.
Charles Evans, in a fit of anger, turned Yeoman Tina Lawton into an iguana. (TOS: "Charlie X")
Although Yeoman Lawton's transformed configuration can be visibly identified as an iguana, the final draft script of "Charlie X" referred to the creature merely as "a small green lizard."
When Spot was affected by Barclay's Protomorphosis Syndrome, she turned into an iguana-like creature. (TNG: "Genesis")
Doctor Zimmerman created a hologram of an iguana that could speak in a slow, drawn-out low voice. He kept it as a pet, and named it Leonard. (VOY: "Life Line")