Looks like a frog. Swims like a frog. But doesn't croak. A flattened, brown, aquatic species from Borneo has just become the only frog shown to have no lungs.

The species, Barbourula kalimantanensis, is so rare that until last year only two specimens were known to science and no herpetologist had seen it alive

No one wanted to slice the frogs up for dissection, so no one had noticed the absence of lungs.

But last year herpetologists on an expedition to a remote section of Borneo managed to collect more of the frogs

In a fast mountain river

This water, it turns out, is ideal for a lungless frog. "They weren't incredibly hard to catch, but they were incredibly slippery

The cold-water home holds more dissolved oxygen than warm water does

And the water current rushing along at 2 to 5 meters per second steadily renews the oxygen supply