The Green Iguana or Common Iguana (Iguana iguana) is a large, arboreal herbivorous species of lizard of the genus Iguana native to Central, South America, and the Caribbean. Usually, this animal is simply called the iguana. The green iguana ranges over a large geographic area, from southern Brazil and Paraguay as far north as Mexico and the Caribbean Islands especially in Puerto Rico where they are also known as "Gallina de palo" and they are very common throughout the island where it is seen as an intruder animal from South America; and in the United States as feral populations in South Florida (including the Florida Keys), Hawaii, and the Rio Grande Valley of Texas.
A herbivore, it has adapted significantly with regard to locomotion and osmoregulation as a result of its diet. It grows to 1.5 metres (4.9 ft) in length from head to tail, although a few specimens have grown more than 2 metres (6.6 ft) with bodyweights upward of 20 pounds (9.1 kg).
Traditionally, reptiles are members of the class Reptilia comprising the amniotes that are neither birds nor mammals. (The amniotes are the vertebrates with eggs featuring an amnion, a double membrane that permits the embryo to breathe effectively on land.) Living reptiles, in that sense, can be distinguished from other tetrapods in that they are cold-blooded and bear scutes or scales.
Reptiles originated around 320-310 million years ago during the Carboniferous period, having evolved from advanced reptile-like amphibians that became increasingly adapted to life on dry land. Many groups are extinct, including dinosaurs, pterosaurs, and aquatic groups such as the ichthyosaurs. Modern reptiles inhabit every continent with the exception of Antarctica. Several living subgroups are recognized:
Although they have scutes on their feet and lay eggs, birds have historically been excluded from the reptiles, in part because they are warm-blooded. They therefore do not appear on the list above. However, as some reptiles are more closely related to birds than they are to other reptiles — crocodiles are more closely related to birds than they are to lizards — cladistic writers who prefer a more unified (monophyletic) grouping usually also include the birds, which include over 10,000 species. (See Sauropsida.)