Dolphin fossils found in east Japan turn out to be world's oldest of new species

A natural history museum in the eastern Japanese prefecture of Gunma says dolphin fossils in its possession are those of a new species of the Yangtze river dolphin family. It says they are the oldest of their kind in the world.

The fossils were unearthed in 1999 from a geological layer along the Usui River in Gunma's Annaka City. The layer dates back about 11 million years. The fossils are of a dolphin's ear and the top part of its head.

Prompted by a discovery in neighboring Tochigi Prefecture of fossils of a dolphin's head that had similar features, the museum decided to examine both sets of fossils. It concluded that the fossils in its possession are those of a new species of the Yangtze river dolphin family. Its determination was based on the distinctive shape of a dent in a bone located at the back of the mouth and other features.

The museum also found that the fossils discovered in Annaka are the oldest fossils of that family in the world.

The researchers say the new discovery will help shed light on the origins and evolution of the dolphin.

The fossils will be on display at the museum from Saturday through the end of June.

Curator Kimura Toshiyuki says there used to be a sea in Gunma, which is now a land-locked prefecture. He says he hopes visitors will imagine the ancient sea, which is where the dolphins used to swim, as they look at the specimens.

In April, the museum announced that fossils of a whale that have been on display, since the facility opened, are from a new species of the fin whale family.