and they had lungs as well as gills. The transition from these lobe-fins to the earliest tetrapods -- four-legged animals that walked on land -- has long been of intense interest to biologists.

Our lungs bring in oxygen and remove carbon dioxide. But other animals breathe in all sorts of different ways. Fish use gills to get their oxygen, like sharks. Animals like worms breathe right ...

“They are one of the few animals that can regenerate their skin ... Scientists have also documented its ability to breathe with lungs and gills, as well as absorb oxygen through its skin.