Although the bottlenose is the only commercially important member of the family Ziphiidæ, and is consequently the best known, the other species of this strange group are not less interesting. All the ziphioids are characterized by the tail which has no notch in the center and by the one or two pairs of teeth in the lower jaw, near or at the end, which sometimes develop in a most unusual way.
In one species, Layard’s whale (Mesoplodon layardi), the two flat, strap-like teeth in the lower jaw grow upward to a height of eight or ten inches and sometimes bend over the long pointed snout, preventing the animal from opening its mouth more than an inch or two. How the whale feeds when the jaws are thus locked is a mystery.
In one species, Mesoplodon grayi, besides the pair of functional teeth near the end of the lower jaw, a row of small teeth are present on either side, entirely embedded in the gum of the upper jaw. These never appear on the surface, even in the oldest animals, and are similar to the teeth concealed in the upper jaw of the sperm whale. In ancient times they were undoubtedly all well developed, but as the food of the whales changed, and the teeth became of less and less importance, they gradually began to disappear.
The front portion of the skull of all the ziphioid whales is produced in the form of a long cylinder of bone which, although open in the middle in young specimens, gradually fills up by ossification of the central cartilage and eventually becomes of almost flinty hardness.
Because of the extreme solidity of this portion of the skull it fossilizes very perfectly. When digging for the fortifications about the city of Antwerp hundreds of these bones and teeth were found, and many have been taken from the “Red Crag” deposits in England.
Ziphioid whales are evidently an ancient group which was once very widely distributed. They are found today in the greatest numbers in the seas about New Zealand and Australia, but single specimens are continually appearing unexpectedly in almost every part of the world.
Recently a specimen was washed ashore on the coast of New Jersey and the skeleton sent to me for identification. I was surprised to find that it represented a species, Mesoplodon densirostris, which before had been recorded only near New Zealand.
When in Japan in 1910 I saw a photograph of a whale which was said to occur at certain times of the year only in Tokyo Bay, and when a skeleton was finally secured for the American Museum of Natural History, the whale was found to represent an exceedingly rare species, Berardius bairdi, which had been taken only in Alaskan waters.
Thus, it is evident that at the present time we know almost nothing about the distribution of these strange whales. Every year or two new species are being discovered and there is evidence to show that the family, as it now exists, is the last survivor of a once numerous group.