Iguana (/ɪˈɡwɑːnə/, Spanish: [iˈɣwana]) is a genus of herbivorous lizards that are native to tropical areas of Mexico, Central America, South America, and the Caribbean. The genus was first described by Austrian naturalist J.N. Laurenti in 1768. Two species are placed in the genus: The green iguana, which is widespread throughout its range and a popular pet; and the Lesser Antillean iguana, which is native to the Lesser Antilles. Genetic analysis indicates that the green iguana may comprise a complex of multiple species, some of which have been recently described, but the Reptile Database considers all of these as subspecies of the green iguana.
The word "iguana" is derived from the original Taino name for the species, iwana. In addition to the two species in the genus Iguana, several other related genera in the same family have common names of the species including the word "iguana".
The species is a popular quarry for pets, and non-native animals have been widely introduced beyond its native area, into Ishigaki Island, the Florida Peninsula, Hawaii, Singapore, Thailand, Taiwan, and including numerous islands with native Iguana populations in the Lesser Antilles.
Iguanas are large lizards that can range from 1.2 to 2.0 m (4 to 6.5 ft) in length, including their tails. They possess a dewlap and a row of elongated scales running from the midline of their necks down to their tails. Iguanas have varying types of scales covering different areas of their body; for example, some large, round tuberculate scales are scattered around the lateral region of the neck among smaller, overlapping scales. The scales on the dorsal trunk of their bodies are also thicker and more tightly packed than those on the ventral sides.These scales may be a variety of colors and are not always visible from close distances. They have a large, round scale on their cheeks known as a subtympanic shield.
Iguana eating flower.
Iguanas have keen vision and can see shapes, shadows, colors, and movement at long distances. Their visual acuity enables them to navigate through crowded forests and to locate food. They employ visual signals to communicate with other members of the same species.
The tympanum, the iguana's eardrum, is located above the subtympanic shield (or "ear shield") behind each eye.
Iguanas are often hard to spot, as they tend to blend into their surroundings, and their coloration enables them to hide from larger predators
Like most reptiles, an iguana has a three-chambered heart with two atria, one ventricle, and two aortae with a systemic circulation. The muscles of an iguana are very light in color due to the high proportion of fast-twitch, glycolytic muscle fibers (type A). These A fibers are not very vascularized and are low in myoglobin, giving them their pale look. This high density of A fibers allows iguanas to move very quickly for a short period of time, which facilitates short bursts of movement, but is inefficient for long duration movement, since cellular respiration in A fibers is anaerobic.
Several species of lizards, including the iguanas, have a pale scale towards the back of their heads marking the parietal eye. This organ is sensitive to changes in illumination and sends signals to the pineal gland noting the change between day and night. A photopigment commonly found in the lamprey, known as parapinopsin, is also found in the iguana, and is sensitive to ultraviolet light and aids in the signaling between day and night.