280 WHALES 



ancestors of the modern Sperm Whale, e.g. in Diaphorocetus and Idiophonis, 

 fossils of \vhich were found in Lower Miocene deposits in the Argentine. 

 These animals had fourteen and twenty-two upper teeth respectively. 

 Extinct members of the Sperm Whale family from the Miocene deposits 

 found near Antwerp, e.g. Scaldicetus caretti and Physeterula of which the 

 Brussels Museum of Natural History has such remarkable fossils, also had 

 a long row of well-developed teeth in the lower and upper jaws. However, 

 at about that period, the animals had already begun to concentrate on a 

 diet of cuttlefish. Thus different fossils dating from within the last 

 ten million years or so had first a continuous groove and subsequently 

 nothing but a few rudimentary teeth in the upper jaw. The teeth of 

 Placoziphhis from the Miocene deposits of Belgium and Holland had 

 probably begun to be very much like those of modern Sperm Whales. 

 Recent Pigmy Sperm Whales have 9-15 small conical teeth on either side 

 of the lower jaw, and occasionally one or two rudimentary teeth in the 

 upper jaw. Pigmy Sperm Whales, too, feed predominantly on cuttlefish, 

 but supplement their diet with crabs. 



The Beluga and the Narwhal, both inhabitants of the Aictic, have a 

 very mixed diet of cuttlefish, shrimps, crabs and fish. Moreover, both 

 types look for their food at the bottom of the sea. The Beluga, whose fish 

 diet consists largely of flounders and plaice, also feeds on halibut, capelin 

 and salmon. It has a fairly good set of from 8-10 teeth on either side of the 

 jaw. The Narwhal (Fig. 40), on the other hand, is completely devoid of 

 teeth, and seizes its prey with the hard edges of its jaw, swallowing it 

 without chewing - like all other Odontocetes. Narwhal embryos, however, 

 have two tooth-buds on either side of the upper jaw, behind which are 

 found four dental papillae, which may occasionally develop into small 

 teeth completely covered by gum. In bulls, one of two left tooth-buds 

 generally develops into the eight-foot spiral tusk, though, occasionally, 

 the tusk can develop from one of the buds on the right side. Moreover, 

 there are also known cases of Narwhals with two tusks, examples of which 

 can be seen in the Zoological Museums of Stockholm, London and 

 Amsterdam. There are some known cases of a cow having a tusk - their 

 tooth-buds, however, rarely break through the gum. In any case their 

 lack of tusks seems to be no disadvantage, since Freuchen, who made a 

 thorough study of Greenland Narwhals, showed that the males use their 

 tusks neither for attack nor for defence. They never break the ice with 

 them either, and during fights in the mating season they are very careful 

 not to get this 'weapon' damaged. It is very fragile, indeed, and once it 

 snaps, infection can set in very quickly. The fragility of the Narwhal tusk 

 is due to the fact that its pulp cavity, which contains living tissue, runs 

 right to the tip of the tusk, whereas in the tusk of, say, the elephant, it 



