Dolphin which imprisoned fish 22 million years ago found in New Zealand

A newly discovered prehistoric dolphin appears to have had a unique method for catching its prey.

Aureia rerehua was found in the Hakataramea Valley in the South Canterbury region of New Zealand’s south island. It was uncovered in a limestone quarry in a layer of sediment that dates to 22–23 million years ago (mya).

It is described in a paper published in the Journal of the Royal Society of New Zealand.

This places the newly discovered dolphin species right on the temporal boundary between the Oligocene epoch (34–23 mya) and the Miocene (23–5.3 mya). This period of Earth’s history was warmer and wetter than today.

New Zealand sank between 22 and 27 mya, leaving only 1% of the islands above the surface. This saw a blossoming of marine life in the region.

A. rerehua is most similar to an extinct dolphin and a toothed whale from the late Oligocene – Waipatia and Otekaikea, also found in New Zealand. Partial fossils found in Australia and Europe have been given the taxonomical designation ‘waipatiid’.

The new dolphin is known from a very well-preserved skull.

One feature of the skull caught the palaeontologists’ eyes: spread out and splayed teeth. They suggest that the dolphin could have hunted in a unique way.

Dolphin skull in rock on white background with scale
Aureia fossil block. Credit: Shane Meekin.

The researchers theorise the dolphin could have swept through schools of fish in shallow waters. Closing its mouth, it could have trapped its prey against its splayed teeth.

Different hunting techniques between Aureia and other extinct dolphins in the region suggest “a divergence of the function of their teeth and the possible feeding strategies employed to catch prey,” the authors write.

Comparable teeth can be seen in prehistoric marine reptiles like Plesiosaurus, the researchers note. In these animals, they are adapted for piercing small or soft prey.

“Though less tightly packed than the teeth of these filter feeding reptiles, the spaced teeth of A. rerehua might still have caged small fish, innovating a unique feeding strategy among odontocetes,” they add.

The creature’s scientific name Aureia rerehua, comes from Māori words. Aureia comes from the word “aurei” meaning “cloak pin,” referring to the shape of its teeth. “Rerehua” means “beautiful,” referring to the stunning preservation of its skull.

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