A new member of fossil balaenid (Mysticeti, Cetacea) from the early Pliocene of Hokkaido, Japan.

The family Balaenidae includes two genus and four extant species. Extinct balaenids are known for at least four genus and 10 species. The oldest known record of members of the Balaenidae is known from the early Miocene, but still need more early members of the family to provide better phylogenetic hypotheses. FCCP 1049 from the lower part of the Chippubetsu Formation, Fukagawa Group (3.5-5.2 Ma, Zanclean, early Pliocene) was preliminary described and identified as sp. by Furusawa and Kimura in 1982. Later works discussed that FCCP 1049 is different from the genus, and is placed in different clade from . The result of our phylogenetic analysis places FCCP 1049 basal to , and is again separated from In this study, FCCP 1049 is re-described and named as gen. et sp. nov. is distinguishable from other balaenids by having a deep promontorial groove of the pars cochlearis of the periotic. can be differentiated from other balaenids, except by having a slender zygomatic process, and posteriorly oriented postorbital process in dorsal view. adds detailed skull, periotic and bulla morphologies for the earlier balaenids.