These frogs do not have the adhesive toe disc cups found in the tree frogs. The family is broken up into three sub-families: Limnodynastinae, Myobatrachinae and Rheobatrachinae. This separation is based mainly on their egg-laying habits. Those of the sub-family Limnodynastinae lay foam nests. The female makes foam with a chemical on her skin. The foam may float on top of water, or be on land. The sub-family Rheobatrachinae has the two species of gastric-brooding frog, and the rest are in the sub-family Myobatrachinae.