Previously the only four-limbed creatures known to lack lungs were salamanders.
A species of earthwormlike, limbless amphibian called a caecilian is also lungless.
Tetrapods, or four-limbed creatures, that develop without lungs are rare evolutionary events, Bickford and colleagues write.The researchers suggest lunglessness in B. kalimantanensis may be an adaptation to the higher oxygen content in fast-flowing, cold water.
"Cold water can hold more dissolved oxygen than warm water," Bickford explained.
The frog also has a low metabolic rate, which means it needs less oxygen.
What's more, the species is severely flat compared to other frogs, which increases the surface area of the skin.
"Along with the fact that having lungs makes you more likely to be swept away in a fast-flowing stream—because you would float—this [is] a very strong context for the evolution of loss of lungs," Bickford said.
(Article from National Geographic Website)