Everything about Spade-toothed Whale totally explained
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 Hector and described the next year by
John Edward Gray who named it honor of
Henry Hammersley Travers, the collector. This was eventually lumped with
Layard's Beaked Whales, 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's likely to be the most poorly known large mammalian species of our time.
Physical description
Nothing is known about this species other than cranial and dental anatomy. There are some notable differences between 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's 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.
Population and distribution
This species has been found in the eastern and western Pacific, although it hasn't been found in between. Considering the fact that the specimens must have been drifting in surface
ocean currents before being deposited, it's more likely than not that they originated somewhere in the southern Pacific - perhaps from NE of New Zealand to the Central Pacific - at a latitude around the
Tropic of Capricorn. As nothing is known about how long the dead whales had been drifting before they were washed ashore, nothing can be said with certainty however.
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 from 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's unlikely to be abundant.
Specimens
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 isn't known. It could, in theory, be resolved though - the sex by recovering or failing to recover DNA sequences of the Y chromosome. Note that little material is shared between the Pitt Island specimen and the calvariae, making direct anatomical comparisons problematic.
Further Information
Get more info on 'Spade-toothed Whale'.
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