Size. Males 580 mm SVL, 2010 mm TL; females 410 mm SVL, 1440 mm TL. The largest lizard in T&T and the western hemisphere. Snout blunt, head rectangular, body robust, a large pendulous dewlap, and a vertebral crest with the tallest spines on the nape will readily distinguish it from all other lizards. The body is covered with small, quadrangular, imbricate, keeled scales; ventral scales larger than dorsals. Adults usually green but may be gray, red, tan, or blue with obscure transverse bands; pale green beneath. Juveniles may be confused with adult Polychrus, which has a pointed snout and large plate like scales on the top of its head and moves slowly, iguanas are very fast.
This lizard is relatively common in urban areas with large trees. Juvenile cohorts may stay together, terrestrial during the day, arboreal at night; adults may be solitary or in colonies, along streams or ponds; may use urban parks or tree plantations; also in secondary and primary forests. Escape response is to dive into water from perch when disturbed. Iguanas are strict herbivores and they have special chambers in their digestive system for processing difficult to digest plant material. Reproduction. Males turn gold or red-orange during breeding season. A month of courtship precedes copulation, usually in early dry season; females construct a nest burrow, these may be communal shared with each female depositing eggs in a separate camber, clutch sizes average about 35 eggs; incubation is 65 to 115 days; hatchlings 70-80 mm; maturity reached in the second or third year at about 250 mm SVL. Predators. Snakes, raptors, cats, coatis, tyra, and humans are predators. If restrained they will bite and lash tail.