AUSTRALIA has a new mammal. Scientists have discovered a previously unknown dolphin swimming in the nation's southern waters.

Until now it had been thought the world had just two species of bottlenose dolphins. The common bottlenose, generally at home in offshore waters, and the more coastal Indo-Pacific species, are both found near Australia.

However, Macquarie and Monash university researchers, collecting genetic samples from what they thought were coastal dolphins, made an unexpected find. After DNA testing about 200 mammals off Victoria, South Australia and Tasmania for a population study, the scientists realised they were not coastal bottlenose dolphins at all.

Such finds, said Dr Moller, were "pretty rare". "Large mammals are not discovered very often. It shows we still have a lot to learn about how many marine species are out there.

Dr Moller said she believed the limited range of the new species meant it deserved special protection.