The Spiny-Tailed Iguana has a dark heavy body with a shorter tail ringed with rows of sharp curved spines. When mature the male has a very great crest, a wide head and strong jaws whereas the female is smaller with a narrow head. Adults may grow to 4 feet in length. They are excellent climbers and prefer a rocky habitat with plenty of crevices to hide in, rocks to bask on, and nearby trees to climb