http://www.digitaljournal.com/science/oldest-dolphin-gets-a-new-name/article/384233

Oldest dolphin gets a new name

Posted May 20, 2014 by Tim Sandle
A dolphin, first described from a fossil skull discovered in the 1970s, has been given a new name. However, the mammal retains the title of oldest true dolphin species identified to date.
This is the skull of the holotype of Eodelphis in lateral view.
This is the skull of the holotype of Eodelphis in lateral view.
Mizuki Murakami
The dolphin is now called Eodelphis kabatensis. The dolphin swam the seas 8.5 million to 13 million years ago. This is a few million years before ancestors of spinner dolphins and others in the Stenella genus evolved.
According to the Daily Mail, the skull of Eodelphis kabatensis was originally collected from a small tributary of the Oshirarika River on the island of Hakkaido, Japan.
Scientists have decided that the older creature should not have been a part of the Stenella genus and needed a new name. Giving E. kabatensis a new name can also reconcile the gap between molecular studies showing that true dolphins started to diversify 9 million to 12 million years ago and other fossil evidence dating the emergence of the animals to only 6 million years ago.
The re-naming of the dolphin was reported to the Journal of Vertebrate Paleontology, in a report rather lengthily titledEodelphis kabatensis, a new name for the oldest true dolphin Stenella kabatensis Horikawa, 1977 (Cetacea, Odontoceti, Delphinidae), from the upper Miocene of Japan, and the phylogeny and paleobiogeography of Delphinoidea.”