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The spade-toothed whale (''Mesoplodon traversii'') is a very little-known and the rarest species of beaked whale. It was first named from a partial jaw found on Pitt Island, New Zealand, in 1872; reported and illustrated in 1873 by James Hector, and described the next year by John Edward Gray, who named it in honor of Henry Hammersley Travers, the collector. This was eventually lumped with the strap-toothed whale, starting as early as an 1878 article by Hector, who never considered the specimen to be specifically distinct. A calvaria found in the 1950s at White Island, also New Zealand, initially remained undescribed, but was later believed to be from a ginkgo-toothed beaked whale. In 1986, a damaged calvaria was found washed up on Robinson Crusoe Island, Chile, and was described as a new species, ''Mesoplodon bahamondi'' or Bahamonde's beaked whale.〔Reyes, J.C.; van Waerebeek, K; Cárdenas J.C. & Yáñez, J.L. (1995): ''Mesoplodon bahamondi'' sp.n. (Cetacea, Ziphiidae), a new living beaked whale from the Juan Fernández Archipelago, Chile. ''Boletin del Museo Nacional de Historia Natural, Chile'' 45: 31–44.〕 In December 2010, two specimens, a cow and calf, were found stranded on Opape Beach, Bay of Plenty, New Zealand. They were originally identified as Gray's beaked whale, but later genetic analysis revealed that they represented the first complete specimens of the spade-toothed whale.〔Platt, John R. (Amazing: Rarest Whale Seen for First Time in History, but Not at Sea ). Scientific American Blogs, 5 November 2012.〕 Following this find, a report describing the spade-toothed whale and an analysis of their DNA later appeared in the 6 November 2012 issue of the journal ''Current Biology''.〔 〕 The results of DNA sequence and morphological comparisons have shown all three finds came from the same species, which is therefore properly known as ''M. traversii''.〔van Helden, Anton L.; Baker, Alan N.; Dalebout, Merel L.; Reyes, Julio C.; van Waerebeek, Koen & Baker, C. Scott (2002): Resurrection of ''Mesoplodon traversii'' (Gray, 1874), senior synonym of ''M. bahamondi'' Reyes, van Waerebeek, Cárdenas and Yáñez, 1995 (Cetacea: Ziphiidae). ''Marine Mammal Science'' 18 (3):609–621. (PDF fulltext )〕 The external appearance was only described in 2012, and it is likely to be the most poorly known large mammalian species of modern times. ==Physical description== Until 2012, nothing was known about this species other than cranial and dental anatomy. There are some differences between it and other mesoplodonts, such as the relatively large width of the rostrum. Its appearance might be most similar to an oversized ginkgo-toothed beaked whale in overall shape, as their skulls are quite alike except in size. The distinguishing character are the very large teeth, 23 cm (9 inches), close in size to those of the strap-toothed whale. The teeth are much wider than those of the strap-toothed, and a peculiar denticle on the tip of the teeth present on both species is much more pronounced in the spade-toothed whale. The common name was chosen because in life the part of the tooth that protrudes from the gums, (unlike the strap-like teeth of strap-toothed whales) has a shape similar to the tip of a flensing spade as used by 19th-century whalers. Despite the rather similar dentition, the spade-toothed whale and strap-toothed whale seem to be only distantly related. The present species' relationships are not known with certainty, though, because this species is very distinct morphologically, and the DNA sequence information is contradictory and is currently not good enough to support a robust phylogenetic hypothesis.〔〔Dalebout, Merel L.; Ross, Graham J.B.; Baker, C. Scott; Anderson, R. Charles; Best, Peter B.; Cockcroft, Victor G.; Hinsz, Harvey L.; Peddemors, Victor & Pitman, Robert L. (2003): Appearance, Distribution, and Genetic Distinctiveness of Longman's Beaked Whale, ''Indopacetus pacificus''. ''Marine Mammal Science'' 19 (3): 421–461. (PDF fulltext )〕 Judging from the size of the skull, the species was thought to be between 5.0 and 5.5 meters (16 and 18 feet) in length, perhaps a bit larger. The only known complete specimens are a 5.3 m (17.4 ft) adult female and her 3.5 m (11.5 ft) male calf. The cow was spindle-shaped, with a triangular dorsal fin with a concave trailing edge set about two-thirds the way back. It was dark gray or black dorsally and white ventrally, with a light thoracic patch created by a diagonal band that extends from behind the eye downwards and back to the dorsal fin. It also has a dark eye patch, rostrum, and flippers.〔 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「Spade-toothed whale」の詳細全文を読む スポンサード リンク
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