The Spade-toothed Whale, Mesoplodon traversii, was a name given to a partial beaked whale jaw found on Pitt Island (New Zealand) in 1872 figured 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 Layard's Beaked Whale, starting as early as 1878 (Hector 1878, who in fact never considered the specimen to be specifically distinct). A calvaria found in the 1950s at White Island (also New Zealand) initially remained undescribed but later was believed to be from a Ginkgo-toothed Beaked Whale (Baker & van Helden 1999).
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. The results of DNA sequence and morphological comparisons (van Helden et al. 2002) have shown that all three finds come from the same species, which is therefore properly known as M. traversii. This species is remarkable since the external appearance is still completely unknown, and it is likely to be the most poorly known large mammalian species of our time.
Nothing is known about this species other than cranial and dental anatomy. There are some notable differences between it and other mesoplodonts, such as the relatively large width of the rostrum; altogether it might look 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 of the animal, 23 cm (9 inches), close in size to those of Layard's Beaked Whale. The teeth are much wider than the Layard's, 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 the part of the tooth that protrudes from the gums in life, unlike the straplike ones of Layard's Beaked Whales, must have a shape similar to the tip of a flensing spade of 19th-century whalers.
Despite the rather similar dentition, the Spade-toothed Whale and Layard's Beaked Whale seem only distantly related. The present species' relationships are not known with certainty though, because it is very distinct morphologically and DNA sequence information is contradictory and unable to propose a robust phylogenetic hypothesis this far. Judging from the size of the skull, the species may be between 5 and 5.5 meters (16 and 18 feet) in length, perhaps a bit larger.
Ecology and status
This species has never been seen alive, so nothing is known of its behavior. It is presumably not different from other Mesoplodon of medium size, which are deep-water species living alone or in small groups and which feed on cephalopods and small fish. The young become independent of their mothers probably around one year of age, as in most whales.
The population status of the Strap-toothed Whale is entirely unknown, but it is unlikely to be abundant.
- NMNZ 546 - 1872; Pitt Island specimen. Apparently male, probably fully adult.
- Auckland University School of Biological Sciences MacGregor Collection (unnumbered) - 1950s White Island specimen. Probably fully adult.
- MNHNC 1156 - 1986; Robinson Crusoe Island specimen. Probably fully adult.
The sex of the 20th-century specimens is not known. However, by recovering or failing to recover DNA sequences of the Y chromosome, it could, in theory, be resolved. Note that little material is shared between the Pitt Island specimen and the calvariae, making direct anatomical comparisons problematic.
- Tropical Bottlenose Whale, another rare whale
- Baker. Alan N. & van Helden, Anton L. (1999): New records of beaked whales, Genus Mesoplodon, from New Zealand (Cetacea: Ziphiidae). Journal of the Royal Society of New Zealand 29(3) :235–244. PDF fulletxt
- 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
- Gray, John Edward (1874): Notes on Dr Hector's paper on the whales and dolphins of the New Zealand seas. Transactions of the New Zealand Institute 6: 93–97. PDF fulltext. Although the paper was presented in 1873, it was not available in print until the next year.
- Hector, James (1873) On the whales and dolphins of the New Zealand seas. Transactions of the New Zealand Institute 5: 154–170. PDF fulltext. Although the paper was presented in 1872, it was not available in print until the next year.
- Hector, James (1878): Notes on the whales of the New Zealand seas. Transactions of the New Zealand Institute 10: 331–343. PDF fulltext. Although the paper was presented in 1877, it was not available in print until the next year.
- Perrin, William F.; Wursig, Bernd & Thewissen, J.G.M (eds.) (2002): Encyclopedia of Marine Mammals. Academic Press. ISBN 0-12-551340-2
- Reeves, Randall R. & Leatherwood, S. (1994): Dolphins, porpoises and whales: 1994-98 Action plan for the conservation of cetaceans. IUCN, Gland, Switzerland. ISBN 2-8317-0189-9
- 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.
- 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
- ^ Taylor, B.L., Baird, R., Barlow, J., Dawson, S.M., Ford, J., Mead, J.G., Notarbartolo di Sciara, G., Wade, P. & Pitman, R.L. (2008). Mesoplodon traversii. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 24 March 2009. Database entry includes a brief justification of why this species is of data deficient.
- ^ Compare for example van Helden et al. (2002) and Dalebout et al. (2003).
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