Tuatara: Volume 21, Issue 3, April 1975
On Vestigial and Normal Teeth in the Scamper-Down Beaked Whale, Mesoplodon Grayi
On Vestigial and Normal Teeth in the Scamper-Down Beaked Whale, Mesoplodon Grayi
The New Zealand Zoologist J. von Haast, (1876a), in his description of the species of Beaked Whale Mesoplodon grayi, noted as one of the characteristics of the new species the presence of rather large vestigial maxillary teeth. The occurrence of these teeth in Beaked Whales had already been noted (for a detailed review, see Boschma, 1951), but they are so small that they are generally over looked. In Mesoplodon grayi, however, the maxillary teeth were so conspicuous (lengths up to 12 mm) that von Haast (1876b) concluded that the maxillary teeth (17 to 22 teeth in each row) were functional and not vestigial and therefore proposed a new genus Oulodon to contain his species grayi. However Moore (1968), in his recent taxonomic review of the Beaked Whales, did not recognise Oulodon as a genus, not even as a subgenus.
In later descriptions of stranded Scamperdown Beaked Whales, the rather large maxillary teeth had been recorded (for reviews, see Boschma, 1950 and 1951) and more recently Baker (1972), like von Haast (loc. cit.), cited the size of the maxillary teeth as being one of the characteristics of the species. It is, however, less known that in Mesoplodon grayi (as in a number of other Beaked Whales) vestigial teeth can also be found in the lower jaw.
It seems that they are not present in every specimen but when present are much smaller than the maxillary teeth. (See Fig. 1, specimen 2, at right.)
Recently I had the opportunity to dissect three Scamperdown Beaked Whales. On February 6, 1974, a male specimen, 356.8 cm long, was found in the Port of Napier as was also on the same day at the same locality a female, 373.4 cm long. The next day, in the Port of Napier there occurred a third specimen Mesoplodon grayi, again a male, 398.8 cm long. It is tempting to speculate on the cause or causes of these three strandings at the same date but such is outside the scope of this short paper.
In the dorsal fin of one of the Scamperdown Whales I found, near the posterior rim, a circular hole, looking like a healed wound made by a rifle bullet. As it seemed very unlikely to me that somebody had really taken a shot at the animal, I wondered what had caused the hole — a parasite perhaps? According to Mr. G. P. van Andel (in verbis) this type of hole is often found in the flippers, flukes and dorsal fins of Baleen Whales and Sperm Whales in the Antarctic.
References
Baker, A. N., 1972: New Zealand Whales and Dolphins. Tuatara 20 (1): 1-49. (Also distributed as separate booklet.)
Boschma, H., 1950: Maxillary teeth in specimens of Hyperoodon rostratus (Müller) and Mesoplodon grayi von Haast stranded on the Dutch coasts. Proc. Kon. Ned. Akad. Wetenschappen 53 (6): 775-786, 4 pls.
—, 1951: Rows of small teeth in ziphioïd whales. Zool. Mededelingen 31 (4): 139-148, 1 pl.
Haast, J. von, 1876a: On a new Ziphioid Whale. Proc. zool. Soc. London: 7-13.
—, 1876b: Further notes on Oulodon, a new genus of Ziphioid Whales from the New Zealand seas. Proc. zool. Soc. London: 457-458.
Moore, J. C., 1968: Relationships among the living genera of Beaked Whales, with classifications, diagnoses and keys. Fieldiana (Zool.) 53 (4): 209-298.