Hydrosaurus

(sail lizards), a genus of reptiles of the family Agamidae. Sail lizards reach a length of 110 cm. The body and the long, thick tail are laterally compressed. A ridge of large, flat scales extends along the neck and spine. The half of the tail closest to the body is crested by a leathery fold covered with small scales. In males, the crest reaches a height of 10 cm, whereas in females it is poorly defined. Long ossified protuberances of the tail vertebrae hold the fold in a vertical position, giving it the appearance of a sail.

There are three species of sail lizards, distributed on the islands of Southeast Asia from the Philippines south to Sulawesi and New Guinea. The lizards dwell in trees and shrubs near rivers. When pursued, they are able to dive and hide under rocks. Sail lizards feed primarily on leaves and fruit; occasionally they prey on small invertebrates. The reptiles are egg layers. The meat of sail lizards is eaten by the local population.