Mass: 4 to 9 kg.
Iguana iguana can weigh up to 18 pounds and can reach a length of 5-7 feet. Iguana species can often be identified based on small but constant differences, such as the number of scales below the eyes or size of scales between the eyes. Iguana iguana has a long body, long tail, and short legs. It has a greenish-gray color and can change color slightly (but not nearly as well as some squamates, such as chameleons). A juvenile iguana is much brighter green than an adult. Soft leathery scales cover the body of an iguana. It has feet with 5 very long toes with sharp claws on the ends, used especially for climbing. The iguana has a row of spines that extends along its back from the base of its head all the way to the tip of its tail, descending in size from head to tail. It also has a dorsal crest at the base of its head, and a dewlap underneath its chin. The iguana also has a row of sharp serrated teeth. The male iguana is larger than the female, and has a larger dewlap as well. The male may develop a dorsal crest as high as 3 inches. He has broader jowels, and a bulge behind the cloacal vent, which contains the hemipenes. It is often hard to tell the sex of juvenile iguanas until these characteristics develop. Another way to identify sex when iguanas are older is by examining their femoral pores, which are much different between sexes. During breeding months, secretory activity peaks, and at that time dominant breeding males produce more secretion than subordinates and females. Juvenile males that preform visual displays have significantly larger pores than those who do not display. Because of this, it is believed that there is a relationship between social dominance and androgen levels. Femoral pores are also a good way to identify related species. Related species have secretions that are more similar than distantly related species.