''Miophocaena nishinoi'' is an extinct species of

porpoise Porpoises are a group of fully aquatic marine mammals, all of which are classified under the family Phocoenidae, parvorder Odontoceti (toothed whales). Although similar in appearance to dolphins, they are more closely related to narwhals an ...

from the

Late Miocene The Late Miocene (also known as Upper Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch, which lasted from 11.63 Ma (million ye ...

Koetoi Formation of Japan, dating to around 6.4–5.5

million years ago The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago). ...

(mya), represented by a partial skull. the genus name derives from

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic peri ...

''mio'' for the Miocene, and ''phocaena'' for "porpoise"; the species name honors the discoverer, Takanobu Nishino. ''Miophocaena'' resides in a clade with '' Archaeophocaena'' discovered in the same area, and, along with '' Pterophocaena'', represents an intermediate phase between porpoises and dolphins.

References

Porpoises Mammals described in 2012 Pliocene mammals of Asia {{paleo-whale-stub