HISTORY OF WHALES 



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braincase, almost equal to the length of 

 the rostrum; a strongly attentuated ros- 

 trum, whose extremity is formed by the 

 premaxillaries, 2.7 teeth in each upper 

 jaw, and z6 in each mandible. The 

 crowns of the teeth are recurved, with 

 rugose enamel, and distinct carinae on 

 anterior and posterior cutting edges; 

 posterior teeth with one or more accessory 

 cusps; the roots are slender, gibbous below 

 the crown, and have a large pulp cavity. 

 The skeleton is a few inches longer than 

 that of Kentriodon. The living porpoise 

 Cephalorhynchus may have descended from 

 some such type as Delphinodon. 



There were other species of Upper 

 Miocene porpoises whose skulls were 

 undergoing a process of remodeling lead- 

 ing up to the extremely short-snouted 

 living porpoises, such as Neomeris, 

 Phocaena, and Phocoenoides. An enlarge- 

 ment of the braincase caused the posterior 

 cranial elements to swell outward. 

 Earlier porpoises have the occipital region 

 more or less flattened in contrast to the 

 decidedly bulging appearance of the hinder 

 cranial region of most living delphinoids. 

 This tendency toward enlarging the brain- 

 case resulted in further changes in the 

 relations of certain bones. The facial 

 region becomes broader and the tendency 

 toward shortening and broadening the 

 rostrum becomes more noticeable in some 

 forms than in others. This is particularly 

 true of the section of the delphinoids to 

 which the living "blackfish," Globicephala, 

 belongs. Porpoises with moderately long 

 beaks are in the minority, in so far as 

 genera are concerned, in the existing 

 pelagic faunas. 



Short-snouted porpoises, with skulls 

 that resemble those of Tursiops and 

 Delphinapterus, have been found at a 

 number of localities of Pliocene age in 

 Italy. The relations of the pterygoid 

 and alisphenoid bones are the critical 



structural features that distinguish these 

 two genera, and it is unfortunate that 

 these details have not been ascertained. 

 These Pliocene porpoises had not more 

 than 66 teeth, while the living bottlenose 

 porpoise, Tursiops, has a hundred or more. 

 The trend of development in later Tertiary 

 involves a secondary reduction of the 

 quadrupled or quintupled dentition, and 

 there is no evidence to indicate that recent 

 porpoises are reversing their evolution 

 again by undergoing an increase in the 

 number of teeth. It is more likely that 

 these Pliocene porpoises represent another 

 line of development and that their de- 

 scendants had the teeth further reduced. 

 It is still uncertain whether or not the 

 living white whale, Delpbinapterus, which 

 has a total of 36 teeth, is related to any 

 of these Pliocene porpoises. 



The Lower Pliocene or Plaisancian 

 stage of Italy has at least three species of 

 extinct porpoises that have been referred 

 to Tursiops. Of these the nearly complete 

 skeleton of Tursiops cortesii ([Fischer, 18x9; 

 Cuvier, 1836, pi. ZZ4, Figs, i-z) found 

 south of Fiorenzuola, Italy, is probably 

 the most interesting. This has a skull 

 with 14 teeth in each upper jaw and 14 

 in each mandible. Coming to the Middle 

 Pliocene or Astian stage, we find a larger 

 number of occurrences of extinct porpoises 

 referred to Tursiops. A remarkably well 

 preserved skull and skeleton of Tursiops 

 capellini (Sacco, 1893) found near Cortaz- 

 zone in the Territory of Camerano- 

 Carasco, Italy, has 16 teeth in each upper 

 jaw and 15 in each mandible. In both 

 of the skeletons just mentioned the atlas 

 and axis are fused together. 



In the late Pliocene or Sicilian stage 

 another species, Tursiops osennae (Simon - 

 elli, 191 1) makes its appearance. This 

 extinct porpoise has zi teeth in the 

 upper jaw and probably an equal number 

 in the mandible. It was found in a 



