EVOLUTION AND EXTERNAL APPEARANCE 75 



known which can be fitted into the modern sub-orders. These were dis- 

 covered mainly in the second half of the nineteenth century dvuing 

 excavations near Antwerp, and also in some eastern parts of Holland. Only 

 recently, thirty pupils at a technical school in Hengelo, led by their 

 teacher, dug up an almost coniplete vertebral column of a fossil whale 

 from a pit at Neede. The Brussels Museuin of Natural History has a parti- 

 cularly fine collection of such fossils. Pliocene Right Whales were 16-50 

 feet long and, ev^en in this respect, strongly resembled some modern whales, 

 for the Pigmy Right Whale has a maximum length of 20 feet. But the 

 Rorquals were still very much smaller than their modern representatives 

 (10-50 feet as against 30-100 feet). During the last few million years of the 

 earth's history, these whales increased their size, so much so that in 

 ancient times it would hardly have been worth the trouble to go whale- 

 hunting on a large scale. In any case, because he appeared only half 

 a million years ago, man could never have met live species of these 

 animals. 



The oldest known representatives of the Odontocetes come from the 

 Upper Oligocene, and cannot, therefore, be more than 30 million years 

 old. They belonged to the Squalodontidae, so-called because their jagged 

 teeth strongly resemble those of the shark (Figs. 39, 148). In the older 

 representatives of this group, the nostrils still lay much further to the 

 front than they do in modern Odontocetes, but the more recent members 

 were practically indistinguishable from our own kind. The size of their 

 brain was smaller than that of modern Odontocetes, bvit considerably 

 larger than that of Patriocetus (see page 70) . 



Their skulls were built symmetrically or almost symmetxTcally, and 

 while the same can be said of the skulls of most mammals, Odontocetes 

 form a rather strange exception to this rule. Externally, these animals are 

 in fact built symmetrically, and their other organs, too, show the bi-lateral 

 symmetry characteristic of normal mammals, man included. However, 

 the blowholes of a number of species are found, not in the centre of the 

 head, but a little to the left. The lack of symmetry in the skull is not 

 equally pronounced in all Odontocetes, but is very striking in, for instance, 

 the Narwhal (Fig. 40) and the Bottlenose Whale, in which the nasal 

 septum is frequently tilted. 



The explanation of this phenomenon has caused experts a great many 

 headaches, but no satisfactory solution has yet been found. We know that 

 this assymmetry was absent or insignificant in the geologically older 

 Odontocetes, and that even during the embryonic development of more 

 recent skulls it occurs fairly late. Clearly, Odontocetes are derived from 

 ancestors with symmetrical skulls, and the change must have occurred 

 during the Miocene, i.e. about 20 million years ago. Apart from the 



