20 million-year-old whale fossils found

The new sub-family of whale has been named tohoraata or "dawn whale".

Two whales, which lived more than 20 million years ago, have been identified by Otago University researchers.

University of Otago palaeontologists identified a previously unknown genus of fossil baleen whales, and two species within it.

The two whales, which lived between 27 million to 25 million years ago, were found preserved in a rock formation near Duntroon in North Otago.

The fossils belong to the toothless filter-feeding family called Eomysticetidae and this was the first time members of this family have been identified in the southern hemisphere.

The new sub-family of whale has been named tohoraata or "dawn whale" by Otago Department of Geology PhD student Robert Boessenecker and his supervisor Professor Ewan Fordyce.

University of Otago geology professor Ewan Fordyce (right) and geology department technician Andrew Grebneff use pneumatic vibrators to carefully uncover the jaw bone of an ancient whale fossil. Photo / Georgina Cousins

They named the younger of the two fossil whales, which may be a descendent of the elder, as Tohoraata raekohao.

Raekohao means 'holes in the forehead' in Maori.

Mr Boessenecker said Tohoraata raekohao lived between 26 to 25 million years ago and was slender and serpent-like.

He said the whale's skull, which contained a number of holes near its eye sockets for arteries, was probably about two metres in length and was eight metres long.

"This new species differs from modern baleen whales in having a smaller braincase and a skull that is generally much more primitive, with substantially larger attachments for jaw muscles.

"The lower jaw retains a very large cavity indicating that its hearing capabilities were similar to archaic whales."

The researchers also determined that another fossil of a whale from the site, which was collected in 1949 and named in 1956, had been misidentified.

The older of the two whales was originally identified as belonging to the genus Mauicetus, a more advanced type of whale.

Only with this study was it proven that this fossil was not from its originally attributed genus, Mr Boessenecker said.

Its name was changed from Mauicetus waitakiensis to Tohoraata waitakiensis.

"Researchers contend with confusing or surprising fossils in museum collections all the time.

"Often, the best way to solve these mysteries is to go out and dig up another one, which is what Professor Fordyce and his colleagues did in 1993 when they collected the partial skull of Tohoraata raekohao."

The study formed part of Mr Boessenecker's thesis and was supported by a University of Otago Doctoral scholarship.