Taxonomy
On 21 February 1819, a 32-ft whale stranded near Grömitz, in Schleswig-Holstein. The Swedish-born German naturalist Karl Rudolphi initially identified it as Balaena rostrata (=Balaenoptera acutorostrata). In 1823, the French naturalist Georges Cuvier described and figured Rudolphi's specimen under the name "rorqual du Nord". In 1828, Rene Lesson translated this term into Balaenoptera borealis, basing his designation partly on Cuvier's description of Rudolphi's specimen and partly on a 54-ft female that had stranded on the coast of France the previous year (this was later identified as a juvenile fin whale, Balaenoptera physalus). In 1846, the English zoologist John Edward Gray, ignoring Lesson's designation, named Rudolphi's specimen Balaenoptera laticeps, which others followed. In 1865, the British zoologist William Henry Flower named a 45-ft specimen that had been obtained from Pekalongan, on the north coast of Java, Sibbaldius (=Balaenoptera) schlegelii — it wasn't until 1946 that the Russian scientist A.G. Tomilin synonymized S. schlegelii and B. borealis, creating the subspecies B. b. schlegelii and B. b. borealis. In 1884-85, the Norwegian scientist G. A. Guldberg first identified the "sejhval" of Finnmark with B. borealis.
Sei whales are rorquals (family Balaenopteridae), baleen whales that include the humpback whale, the blue whale, the Bryde's whale, the fin whale, and the minke whale. Rorquals take their name from the Norwegian word røyrkval, meaning "furrow whale", because family members have a series of longitudinal pleats or grooves on the anterior half of their ventral surface. Balaenopterids diverged from the other families of suborder Mysticeti, also called the whalebone whales or great whales, as long ago as the middle Miocene. However, little is known about when members of the various families in the Mysticeti, including the Balaenopteridae, diverged from each other.
Two subspecies have been identified—the northern sei whale (Balaenoptera borealis borealis) and southern sei whale (Balaenoptera borealis schlegelii). Their ranges do not overlap.
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