Researchers have discovered a new type of dolphin which swam in New Zealand's waters millions of years ago.
Researchers at Otago University found the dolphin fossil in rocks at Cape Farewell, at the top of the South Island, and believe it may be a relative of the ancestors of modern dolphins and toothed whales.
Papahu taitapu lived 19-22 million years ago and was about two metres long - roughly the size of a common dolphin, researchers Dr Gabriel Aguirre and Professor Ewan Fordyce from the university's Geology Department found.
It lived alongside ancient penguins and baleen whales in the warm, shallow sea around Zealandia, or proto-New Zealand.
"Our study of structures of the skull and earbone suggest that Papahu could make and use high frequency sound to navigate and detect prey in murky water.
"They probably also used sound to communicate with each other," Dr Aguirre said.
Few dolphin fossils have been discovered from that time period, making the find more significant, the researchers said.
Although only one specimen of the new dolphin has been found, the skull is distinct from all other reported fossils, meaning the dolphin can be called a new form.
The diverse group of ancient dolphins - including Papahu - evolved and spread around the world 19-35 million years ago, before becoming extinct.
Dr Aguirre said they were replaced by modern dolphins and whales, although no one knows why the ancient sea mammals died out.
