Cryptobranchids are large, salamanders, with large folds of skin along their flanks. These help increase the animal's surface area, allowing them to absorb more oxygen from the water. They have four toes on the forelimbs, and five on the hind limbs. Their metamorphosis from the larval stage is incomplete, so that the adults retain gill slits although they also have lungs, and lack eyelids. They can reach a static size.