 The suborder Cryptobranchoidea contains the primitive salamanders . A number of fossil cryptobranchids have been found , but there are only three living species , the Chinese giant salamander ( Andrias davidianus ) , the Japanese giant salamander ( Andrias japonicus ) and the hellbender ( Cryptobranchus alleganiensis ) from North America . These large amphibians retain several larval characteristics in their adult state ; gills slits are present and the eyes are unlidded . A unique feature is their ability to feed by suction , depressing either the left side of their lower jaw or the right . The males excavate nests , persuade females to lay their egg strings inside them , and guard them . As well as breathing with lungs , they respire through the many folds in their thin skin , which has capillaries close to the surface . 
