The rhinoceros iguana (Cyclura cornuta) is an endangered species of iguana that is endemic to the Caribbean island of Hispaniola (shared by Haiti and the Dominican Republic) and its surrounding islands. A large lizard, they vary in length from , and skin colours range from a steely grey to a dark green and even brown. Their name derives from the bony-plated pseudo-horn or outgrowth which resembles the horn of a rhinoceros on the iguana's snout. It is known to coexist with the Ricord's iguana (C. ricordii); the two species are the only taxa of rock iguana to do so. Taxonomy The rhinoceros iguana is a species of lizard belonging to the genus Cyclura. The rhinoceros iguana's specific name, cornuta, is the feminine form of the Latin adjective cornutus, meaning "horned" and refers to the horned projections on the snouts of males of the species. The species was first identified by Pierre Joseph Bonnaterre in 1789. In addition to the nominate race (C. c. cornuta) found on Hispaniola, the other subspecies is the extinct Navassa Island iguana (C. c. onchiopsis). The Mona ground iguana (Cyclura stejnegeri) from Puerto Rico was originally thought to be a subspecies (and still is by some taxonomists), as Cyclura cornuta stejnegeri. Anatomy and morphology The rhinoceros iguana, like other members of the genus Cyclura, is a large-bodied, heavy-headed lizard with strong legs and a vertically flattened tail. A crest of pointed horned scales extends from the nape of their neck to the tip of their tail. Their color is a uniform gray to brown drab. Most adults weigh . Like all reptiles, rhinoceros iguanas are cold-blooded, meaning they need external sources to heat themselves; they move as the sun shifts in order to get an optimal internal temperature. These iguanas are characterized by the growth of bony prominent tubercles on their snouts which resemble horns. Males possess an adipose pad in the form of a helmet on the occipital region of the head, and a large dewlap. This species, like other species of Cyclura, is sexually dimorphic; males are larger than females, and have more prominent dorsal crests and "horns" in addition to large femoral pores on their thighs, which are used to release pheromones. Distribution and habitat Ranging throughout Hispaniola (in both Haiti and the Dominican Republic), rhinoceros iguana populations are stable only on Isla Beata, and the extreme of the Barahona Peninsula, inside Jaragua