XXVI 



WHALES 



Cohort 3. Mutica 

 Order Cetacea 

 ^Suborder 1. Archaeoceti. Eocene-Miocene 



*Protocetus, Eocene; *Basilosaurus (= *Zeuglodon), Eocene 

 Suborder 2. Odontoceti. Toothed whales. Eocene-Recent 

 *Superfamily 1. Squalodontoidea. Eocene-Miocene 



*Squalodo?i, Miocene 

 Superfamily 2. Platanistoidea. River dolphins. Miocene-Recent 



Platanista, Ganges dolphin, Recent 

 Superfamily 3. Physeteroidea. Miocene-Recent 

 Hyperoodon, bottle-nosed whale, N. Atlantic, Antarctic; 

 Physeter, sperm whale, all oceans 

 Superfamily 4. Delphinoidea. Miocene-Recent 

 Mo?wdon, narwhal, Arctic; Delphinus, dolphin, all oceans; 

 Phocaena, porpoise, all oceans 

 Suborder 3. Mysticeti. Baleen whales. Oligocene-Recent 



Balaenoptera, rorqual, all oceans; Balaena, right whale, 

 temperate and polar seas 



The whales are a successful set of populations of aquatic, carnivorous 

 mammals, which diverged from the eutherian stock, possibly from the 

 creodont branch, at a very remote date. Their specializations for 

 aquatic life involve divergences from the typical mammalian plan 

 greater than those found in any other order, and their organization 

 shows in a remarkable way the effects of habit of life and environment. 

 In many respects the whales have reverted to the characteristics of a 

 fish form of life, most noticeably in the body shape, with elongated 

 head, no neck, and tapering 'streamlined' body. In terrestrial 

 mammals the air resistance is not a serious factor and the body shape 

 does not conform to it, but in water it becomes of first importance. 



The swimming mechanism depends on up-and-down oscillations 

 of the flukes and tail stock, and the efficiency of the system is shown 

 by Gray's demonstration that the power necessary to drag a wooden 

 model of a dolphin through the water with the speed of the animal 

 would necessitate a horse-power in the muscles several times greater 

 than that of any known mammal. Probably in life the accommoda- 



