The Pliocene fossil whale, Eschrichtius davidsonii Cope 1872, is actually a balaenopterid mysticete referable to the modern genus Balaenoptera Lacépède 1804. Redescription of the holotype of B. davidsonii (a partial left dentary), together with the discovery and description of a nearly complete right dentary referrable to this taxon, demonstrates the taxonomic and systematic affinities of Balaenoptera davidsonii.
Although originally thought to be Miocene in age, newspaper accounts of 1872 indicate that the holotype of B. davidsonii was actually collected from fossiliferous sandstones here referred to the San Diego Formation of Late Pliocene age (equivalent to the Blancan North American Land Mammal Age).
Comparisons between the dentary of B. davidsonii and dentaries of other extant and fossil balaenopterids allow recognition of several taxonomically useful mandibular characters (i.e., degree of longitudinal curvature of horizontal ramus and form of transverse cross-sectional outlines). A taxonomic review of other nominal Neogene species of Balaenoptera from Europe and eastern North America is an initial attempt at stabilizing the confusing nomenclatural history and taxonomy of this group. In this regard, the genus Burtinopsis Van Beneden 1872 is placed in synonymy with Balaenoptera.
Generic reassignment of the fossil rorqual Balaenoptera davidsonii (Cope 1872) creates a nomenclatural problem of homonymy with the extant minke whale Balaenoptera davidsoni Scammon 1872. As Cope's species is a senior homonym of Scammon's, suppression of Scammon's name is recommended. The new trinomen Balaenoptera acutorostrata scammoni n. ssp. is here proposed for the North Pacific minke whale.