Dark Is Be j ore the Dawn 353 



Pliocene times. Palaeontologists have come across the teeth, skulls, 

 and skeletons of a number of other completely extinct forms that 

 are of considerable interest. The rights made their first appearance 

 sometime during this period, but rorquals flourished throughout. 

 The best known is called Plesiocetus, of which an almost complete 

 skeleton has been found. One species was sixty feet long. Then 

 there were strange animals apparently halfway between rorquals and 

 rights, typified by one called Mesoteras which had a skull eighteen 

 feet long. But much more extraordinary creatures have been dis- 

 covered in rocks of this age in the extreme south of South America. 

 One was a kind of sperm known as Physodon which had a ten-foot 

 skull with a crest obviously devised to hold a spermaceti tank, but 

 which had twenty-two teeth on either side of the upper jaw, as well 

 as twenty-four in each side of the lower. The shape of the head must 

 have been more like that of the little pigmy sperm than of the greater 

 species living today, since it had a short rostrum, or beak. 



When we reach down into the next level of the rocks, known as 

 the Miocene Period — which lasted from nineteen million to seven 

 million B.C. — we enter for the first time a distinctly different ceta- 

 cean world. Some very primitive rorquals, a sort of generalized group 

 of sperms, and creatures that may be distinguished as ziphioids and 

 true dolphins make their first appearance, but the seas were for the 

 most part populated by Acrodelphids and no fewer than four other 

 families of extinct primitive whales. One of these is known as the 

 Eurynodelphidae, which, being translated, means the "Broadened 

 Dolphins" and is just about the silliest description possible, since the 

 majority of them were pronouncedly the exact opposite. These were 

 the most numerous whales of the time, it would appear, and they 

 were in many ways far ahead of their time. They had long, toothless 

 bills like those of storks, either entirely without teeth or with tooth- 

 less front beaks and numerous teeth in the hinder part of both jaws. 

 Another group we find here for the first time — going backwards, of 

 course — are called the Cetotheres. . 



These are ancient and rather primitive baleen whales, combining 

 many features of all the present-day families of those creatures. Their 

 discovery caused a great deal of debate extending over many years 

 as some palaeontologists thought they had at last found, in them, a 

 missing link between the baleen and the toothed whales. However, 



