XXVI 



PRIMITIVE WHALES 675 



The whales known from the Eocene were different from either of 

 the modern groups and are placed in a separate suborder *Archaeoceti 

 (Fig. 445). The body was very long (up to 70 ft) and apparently 

 thinner than in modern whales, suggesting a sea-serpent form, 

 probably of low swimming efficiency. The hind legs had already disap- 

 peared, though vestiges of their skeleton remained. The skull was 



Fig. 445. Change in position of the blow-hole (nos.) during the evolution of whales. The 

 two upper figures show the condition in the Eocene *Basilosawus, the lower figures a 



Miocene squalodont. 



/. frontal; m. maxilla; n. nasal; />. parietal; pm. premaxilla; sq. squamosal. (Modified after Romer, 

 Man and the Vertebrates, University of Chicago Press.) 



long, the nostril had moved some way back. The teeth were of the 

 normal mammalian number, 44, and were heterodont. The molars had 

 sharp crenated edges, as in other fish-eaters, and the animals were 

 obviously carnivorous, suggesting a possible creodont ancestry. Casts 

 of the brain show large olfactory centres but a small, little folded, 

 cortex. The cerebellum was enormous (if it has been correctly recon- 

 structed). 



These animals, such as *Basilosaiirns (= *Zeuglodon) y had already 

 developed a long way from the main eutherian stock by middle Eocene 

 times. This is an example of relatively rapid evolutionary change; it 

 may be presumed that their ancestors had been in the condition of 

 small insectivores not much later than the end of the Cretaceous, at 

 the most 20 million years earlier. The basilosaur type persisted to the 

 Miocene, but the exact connexions with the two modern sorts of 



