Before scientists went snorkeling in Borneo and plucked a frog, the charming looking Barboroula kalimantanensis, out from under a large rock in a fast moving body of water, the elusive species had been found only twice before. In 1978 Djoko Iskandar described the new species of frog in the journal Copeia (Dec. 28, 564-566), cataloging its webbed toes, rugose skin, flattened head, and the myriad anatomical features that distinguished it as a unique species. The second find was sighting was almost 20 years later, 1995, by the same scientist, Iskandar, who also collaborated on the current research.
As an endangered species, the frog is perhaps lucky that it's so difficult to locate, although it's still subjected to environmental pollutants and habitat encroachment from logging and mining. Not so fortuitous for these primitive frogs, the scientists decided to dissect the specimens for the first time and found that the species has no lungs. David Bickford, an evolutionary biologist at the National University of Singapore, explained that "because these specimens were so rare, they had never been dissected. If you have just one...in your museum, you don't want to rip it open!" (a different approach then some scientists take with their newly found marine species, Acronym Required has found). If unlucky for these frogs, the discovery was lucky for the researchers, as they got their name splashed across headlines around the world. 1
The biologists hypothesize that the frog adapted to the highly oxygenated fast moving water by losing lung capacity. Since the frog lost its lungs, its body became more flattened and less buoyant, which researchers deduce helps it stay under rocks. As well, with its increased surface area respiratory capacity through its increased skin surface area.
Tetrapods without lungs are rare. There are lung-less salamanders and one species of caecilian, an earthworm-like amphibian, that don't have lungs, and some frogs with very diminished lungs, but this is the first species to have only cartilage in the place of lungs.
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1 This news was in an advance press release supposedly ahead of a April 8th Current Biology article which we could not locate. Acronym Required usually doesn't publish research without reading the original source, but will update this post if needed. Update 05/06 - The article was published May 06, 2008 in Current Biology: Bickford, D.; Iskandar D.; Barlian, A; "Lungless frog discovered on Borneo": Current Biology, Vol 18, R374-R375, 06 May 2008.
