Physical characteristics

This large family contains species with varied appearances. Members of the Iguanidae family range from squat, toadlike horned lizards (Phrynosoma spp.) that fit in the palm of a hand, to iguanas (Iguana spp.) that are as long as a man is tall, and long-tailed and sleek anoles often seen climbing on a window screen. However, the family does have one characteristic that sets it apart from the other Iguania families. That trait is pleurodont teeth, which lie in inner-jaw grooves rather than in sockets.

The subfamilies within Iguanidae can be described in more detail. Members of the Iguaninae include the green iguana (Iguana iguana) and marine iguana (Amblyrhynchus cristatus). The typical iguanine is an imposing beast with a strong, muscular tail and (in males) a row of noticeable spines down the center of the back.

The corytophanines and polychrotines are slender-bodied lizards with long tails and long limbs. Corytophanines are generally the larger of the two, ranging in size from about 12 to 25.5 in (30.5 to 64.8 cm), compared to the 3-16 in (7.6-40.6 cm) range in the anole subfamily. The most obvious difference is the casque, or helmet, seen in the Corytophaninae subfamily. The casque is actually a tall fin on the top of the head. Corytophanines also generally have exaggerated dorsal and tail fins.

A pair of green anoles (Anolis carolinensis); male has extended dewlap. (Photo by Animals Animals ©James H. Robinson. Reproduced by permission.)

The crotaphytines and phrynosomatines are the typical lizards associated with southwestern United States. The former, which include the collared and leopard lizards, are quick, long tailed, and fairly large headed. The leopards are noted, and named, for their abundant dorsal spots, and the collared lizards usually display incomplete neck bands. The phrynosomatines are more diverse, and include more hefty-bodied species. Perhaps the most well-known phrynosomatines are the horned lizards (Phrynosoma sp.), which are often mistaken for toads because of their wide bodies and very short limbs.

The final three groups of Iguanidae are the hoplocercines, oplurines, and tropidurines. They are all small to moderately sized lizards. The first group has spiny scales; the second and third groups are distinguished more by geographic distribution (Madagascar for the second, and extreme South American areas for the third) than their appearance.

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