Cutaneous respiration
The skin of amphibians is a major site of respiration in all species for which measurements are available. Cutaneous respiration is the sole respiratory mode of lungless salamanders (family Plethodontidae) which lack lungs entirely yet constitute the largest family of salamanders. Cutaneous respiration in frogs and other amphibians may be the primary respiratory mode during colder temperatures.
Palaeobatrachus
These frogs lived permanently in water. Their bag-shaped lungs, on the dorsal side of their body, enabled them to remain submerged for long periods. They inhabited through-drainage basins or swamps where brown coal deposits were formed. Like the African clawed toad, they probably lived on small crustaceans, insect larvae and small fish and themselves provided sustenance for many other animals.