270 



WHALES 



Figure i§o. Longitudinal section through the 

 teeth of a young and an adult Beluga. E = enamel; 

 C = cement; D = dental bone; P = pulp 

 cavity. {Weber, igsS.) 



tooth-buds found in the connective tissue of the jaws of Mysticete foetuses 

 at a certain stage of their development (see Chapter 2) still resembles the 

 triple crown of the teeth of Archaeocetes, but tooth-buds with more than 

 one cusp do not persist for long (Fig. 149). 



The teeth of Odontocetes have only one single root (Fig. 150). The 

 central pulp cavity is generally fairly small and usually disappears after 

 a time, when no further dental growth can take place. Like the teeth of 

 most other mammals, man included, Odontocete teeth consist of dentine 

 surrounded with cement and covered with an enamel cap. In older 

 animals, the crown is often worn down, so much so that the enamel has 

 completely disappeared to reveal dentine stumps. Enamel is altogether 

 lacking in adult Narwhals, Sperm Whales, Pigmy Sperm Whales and all 

 Ziphiidae with the exception of the Bottlenose Whale, though the 

 ancestors of Sperm Whales must have had enamel crowns, since embryos 

 still have enamel organs in their tooth-buds. Cetaceans do not grow a 

 second set of teeth, i.e. they do not shed their 'baby teeth'. 



'A'lontrez-moi vos defits et je vous dirai qui vous êtes,' the great Cuvier said 

 at the beginning of the last century, and his epigram applies a fortiori to 

 Odontocetes, whose feeding habits are far from uniform. In the first place 

 there are the fish-eaters, e.g. porpoises and most dolphins, the length of 

 whose jaws differs from species to species, though even those with relatively 

 short jaws must be considered long-jawed mammals (Fig. 151). In fresh- 

 water dolphins, the two lower jaws have become fused along almost their 

 entire length, thus providing exceptional rigidity. The number of teeth 

 on each side of upper and lower jaws varies from about fourteen (Irawadi 



