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Omura's whale or the dwarf fin whale (''Balaenoptera omurai'') is a species of rorqual about which very little is known. Before its formal description, it was referred to as a small, "dwarf" or "pygmy" form of Bryde's whale by various sources (including Ohsumi 1978, Wada and Numachi 1991, Carwardine 1995, Perrin et al. 1996, Kahn 2001, LeDuc and Dizon 2002, Kato 2002, among many others). The common name and specific epithet commemorates Japanese cetologist Hideo Omura. The scientific description of this whale was made in ''Nature'' in 2003 by three Japanese scientists. They determined the existence of the species by analysing the morphology and mitochondrial DNA of nine individuals – eight caught by Japanese research vessels in the late 1970s in the Indo-Pacific and an adult female collected in 1998 from Tsunoshima, an island in the Sea of Japan. Later abundant genetic evidence confirmed Omura's whale as a valid species and revealed it to be an early offshoot from the rorqual lineage, diverging much earlier than the Bryde's and sei whales. It is perhaps more closely related to its larger cousin, the blue whale.〔 In the third edition of ''Mammal Species of the World'', the "species" is relegated to being a synonym of ''Balaenoptera edeni''. However the authors note that this subject to a revision of the genus.〔(''Balaenoptera edeni'' ) 〕 The database ITIS lists this as a valid taxon, noting a caveat on the disputed systematics of this species, ''Balaenoptera edeni'' and ''Balaenoptera brydei''. ==Taxonomy== The six specimens obtained in the Solomon Sea in 1976 were only noted to be smaller at sexual maturity than the "ordinary" Bryde's whales caught off New Zealand, whereas the two caught near the Cocos-Keeling Islands in 1978 weren't differentiated from the 118 other "ordinary" Bryde's whales taken in the eastern Indian Ocean, south of Java. As a result of allozyme analysis, their distinctive baleen and small size at physical maturity compared to Bryde's whale, and photographs obtained of the harvested whales (showing their fin whale-like coloration), Dr. Shiro Wada and Kenichi Numachi (1991) decided that these eight individuals represented members of a new species of baleen whale. However, due to the lack of a detailed osteological study and the absence of "conclusive data", the International Whaling Commission (IWC) decided to consider them only as a regionally distinct group of "small-form Bryde's whale". Despite this declaration, the specific status of the Solomon Sea specimens was supported by a mitochondrial DNA study done by Hideyoshi Yoshida and Hidehiro Kato (1999).〔〔Wada, S., & Numachi, K. I. (1991). Allozyme analyses of genetic differentiation among the populations and species of the Balaenoptera. ''Genetic ecology of whales and dolphins''. ''Reports of the International Whaling Commission'', Special (13): 125-154.〕〔 (reprinted on babec.org)〕 The identity of these eight specimens was finally resolved in 1998 when an unidentified whale, which had died after colliding with a fishing boat in the Sea of Japan and was towed to Tsunoshima, was examined by Dr. Tadasu Yamada, Chief of the Division of Mammals and Birds at the National Science Museum, Tokyo. This specimen closely resembled the individuals caught in the 1970s in external appearance and allowed a complete osteological examination of the putative new species to be conducted. As a result of external morphology, osteology, and mitochondrial DNA analysis of two of the harvested whales and the Tsunoshima specimen, Wada, Masayuki Oishi, and Yamada described ''Balaenoptera omurai'' in the 20 November 2003 issue of the journal ''Nature''. In honor of the people of Tsunoshima, who helped remove the flesh from the type specimen, it was given the Japanese vernacular name of "Tsunoshima kujira" (English: ''Horn Island whale'').〔〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Omura's whale」の詳細全文を読む スポンサード リンク
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