The scientific description of this whale was made in the November 20, 2003, edition of Nature (426, 278–281) by three Japanese scientists, Shiro Wada, Masayuki Oishi and Tadasu K. Yamada. The three scientists determined the existence of the species by analysing the morphology and mitochondrial DNA of nine individuals—eight caught by a Japanese research vessel in the late 1970s in the Indo-Pacific and a further specimen collected in 1998 from Tsunoshima 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. The database ITIS lists this as a valid taxon, noting a caveat on the disputed systematics of this species, Balaenoptera edeni and Balaenoptera brydei.
Omura's whale is among the smallest of the rorquals (only the two species of Minke whale are smaller). Of the six specimens taken during Japanese whaling off the Solomon Islands in 1976, the largest adult female was 11.5 metres (38 ft) and the largest adult male 9.6 metres (31 ft). Based on earplug laminations, the former was estimated to be 29-years-old and the latter 38-years-old. Its appearance resembles the larger fin whale, both having the asymmetrical white, right lower jaw, as well as streaks radiating out from the eye region. Its dorsal fin is similar to Bryde's whale, being very falcate and rising at a steep angle; but it is more rounded than the latter species, which usually has a much more pointed fin. Unlike Bryde's, however, they appear to only have one prominent ridge on the rostrum (Bryde's usually have three). It has 80–90 ventral pleats, which extend past the navel. Its 180–210 pairs of baleen plates are short and broad, usually being yellowish-white to black (at times two-tone).
Omura's whale appears to be restricted to the shelf and nearshore areas of tropical and subtropical waters, with records mostly from the eastern Indian Ocean (off Cocos Islands), Indonesia, the Philippines, the Sea of Japan, and the Solomon Sea. On 14 May 2012 an Omura's whale was sighted and photographed off New Caledonia.
Hunting and other mortality
Eight Omura’s whales were taken by Japanese scientific whaling in the 1970s, six in the Solomon Sea in October 1976 and two near the Cocos Islands in November 1978. In the past, artisanal whalers in the Philippines took a sporadic number in the Bohol Sea. Two individuals were also recently incidentally caught in set nets in Japan.
The Omura's whale is listed on Appendix II  of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix II  as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.
In addition, the Omura's whale is covered by the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MOU).
The species may have been sighted off the northwest coast of Australia on two (possibly three) separate occasions in 2009 and 2010. On November 2, 2009 a birder sighted three individuals; the same day another sighting was made north of the Lacepede Islands. In October 2010, sightseers encountered and photographed up to 15 individuals, seeing groups of three or four animals together, as well as at least two cow-calf pairs.
- "Balaenoptera omurai". http://www.iucnredlist.org/apps/redlist/details/136623/0. Retrieved 2012-01-17.
- Jefferson, Thomas, Marc A. Webber, and Robert L. Pitman (2008). Marine Mammals of the World: A Comprehensive Guide to their Identification. London: Academic.
- Wada, S., Oishi, M., and Yamada, T.K. 2003. A newly discovered species of living baleen whale. Nature 426: 278–281.
- Sasaki, T., Nikaido, M., Wada, S., Yamada, T.K., Cao, Y., Hasegawa, M., and Okada, N. (2006). "Balaenoptera omurai is a newly discovered baleen whale that represents an ancient evolutionary lineage". Molecular Phylogenetics and Evolution 41 (1): 40–52. doi:10.1016/j.ympev.2006.03.032. PMID 16843687.
- Balaenoptera edeni Wilson, D. E.; Reeder, D. M., eds. (2005). Mammal Species of the World (3rd ed.). Johns Hopkins University Press. ISBN 978-0-8018-8221-0. OCLC 62265494. http://www.bucknell.edu/msw3.
- "Balaenoptera omura Wada, Oishi, and Yamada, 2003". Integrated Taxonomic Information System. http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=770889.
- Yamada, T. K. 2008. Omura's whale (Balaenoptera omurai), pp. 799–801. In Perrin, W.F.P., B. Würsig, and J. G. M. Thewissen, eds., Encyclopedia of Marine Mammals, 2nd ed. Academic Press, San Diego, 1315 pp.
- Extraordinarily Rare Whale Sighting – Omura’s Whale (Balaenoptera omurai)
- "Appendix II" of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). As amended by the Conference of the Parties in 1985, 1988, 1991, 1994, 1997, 1999, 2002, 2005 and 2008. Effective: 5th March 2009.
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