tem 



tt.rn 



tern 



xxvii. 6 SABRE-TOOTHS 689 



mustelids there is delayed implantation of the blastocyst and other 

 interesting reproductive phenomena. 



The most-modified Carnivora are placed in the superfamily Feloidea. 

 The civets and mongooses (Viver- 

 ridae) (Fig. 458) are survivors 

 that show us many of the charac- 

 ters possessed by this type in the 

 Oligocene. They are the small 

 carnivores that occupy in the 

 Old World tropics the position 

 taken farther north by the weasels. 

 In general they are like the ances- 

 tral miacids, with long skull, 

 small brain, and short legs. Her- 

 pestes, the mongoose, is abundant 

 throughout Africa and Asia. 



The hyenas (Fig. 459) have 

 become large running creatures, 

 with massive teeth specialized 

 for crushing, and hence allowing 

 a scavenging life. The true cats 

 (Felidae) were already differenti- 

 ated from the miacid ancestry in 

 the Eocene, but at that early 

 period they all had the very great 

 development of the upper canines 

 as cutting and piercing sabre- 

 teeth (Figs. 460, 461). There 

 were numerous genera with this 

 characteristic from the Eocene 

 onwards until the Pleistocene, 

 when they disappeared simulta- 

 neously from Europe, Asia, and 

 America. Probably they attacked 

 large, thick-skinned herbivores. 

 The jaw could be opened to a right angle to allow the fang to strike, 

 and there were such associated developments as large mastoid pro- 

 cesses for the sterno-mastoid muscles that pulled the head down- 

 wards and forwards in the strike. The closing muscles of the jaw and 

 the coronoid process were, however, small in the sabre-tooths. 



The cats themselves, with smaller canines, appeared in the Oli- 



Fig. 461. Neck and jaw muscles of A, sabre- 

 tooth, *Smilodon, compared with those of a 

 modern cat B, to show modifications for 

 striking with the whole head and biting, 

 respectively. 



c. condyle; cl. m. cleidomastoid; dig. digastric; 

 m. mastoid process; mas. masseter; st. m. sterno- 

 mastoid; tern, temporalis. (From Lull, Organic 

 Evolution, copyright 191 7, 1929 by The Mac- 

 millan Company and used with their permission, 

 after Matthew.) 



