New Zealand scientists said Wednesday have identified a previously unknown type of fossil dolphin that could be the ancestor of modern dolphins and toothed whales.

Papahu taitapu, the first of its kind ever found, lived 19 million to 22 million years ago, and is one of the few dolphins to be reported globally dating to the start of the Miocene epoch, according to University of Otago researchers.

Judging from the size of its skull, Papahu was about 2 metres long, roughly the size of a common dolphin, and like most living dolphins, it had many simple conical teeth, but its head was probably a bit wider, and not as high-domed, Dr. Gabriel Aguirre said in a statement.

It lived at a time of global warmth, in shallow seas around Zealandia , the continental fragment that New Zealand rests upon, along with ancient penguins and baleen whales.

The skull, one jaw, and a few other parts of Papahu taitapu were found in marine sedimentary rocks in the northern South Island, and only a single specimen had been found so far.

"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," said Aguirre.

Features of the Papahu skull showed it was distinct from all previously-reported fossils, Professor Ewan Fordyce said in the statement.

"When we compared Papahu with both modern and fossil dolphins we found that it belongs in a diverse and structurally variable group of ancient dolphins that evolved and spread world-wide 19 million to 35 million years ago. All of those ancient dolphins including Papahu and others, such as shark-toothed dolphins, are now extinct," said Fordyce.

"They have been replaced by the 'modern' dolphins and toothed whales, which diversified within the last 19 million years."

It was not clear, however, exactly why Papahu and other ancient dolphins went extinct, he added.