Miobalaenoptera numataensis

Miobalaenoptera numataensis is an extinct rorqual from the Late Miocene (Messinian) of Japan and the species described within the genus Miobalaenoptera. It is distinguished from other rorquals, both extinct and living, by features of the earbone, including the periotic, and by strongly diverging basioccipital crests at the base of the skull. The holotype specimen was found in marine deposits in Numata town on Hokkaido, Japan. It was first assigned to Balaenoptera cf. acutorostrata, the minke whale group, by Shinohara in 2012 and thought to be Pliocene in age, but analysis of diatoms in the surrounding matrix and further preparation of the specimen showed that it is late Miocene and a distinct species of extinct rorqual.