310 THEROMORPHA CHAP. 



Dicynodon, with many species from the Karroo formation of 

 South Africa, reached formidable dimensions. The thick, curved 

 skull is in size and outline not unlike that of a large lion, hence 

 D. leoniceps, D. tigriceps, etc. The zygomatic arch is almost 

 mammalian, except that the posterior boundary of the orbit is 

 formed by a distinct postfrontal bone. The nostrils are lateral. 

 The canine tusks (Fig. 54, E, p. 280) are very large. The 

 choanae open behind the rhomboid vomer and between the sepa- 

 rated palatine bones, which are posteriorly confluent with the 

 medially united pterygoids. The latter send out flat extensions, 

 along the lateral side of the palatines ; these extensions reach 

 the maxillaries and probably represent the ectopterygoids. The 

 occipital condyle is distinctly triple, being equally composed of 

 the basi- and latero-occipital bones. 



The three bones of the shoulder-girdle meet at the glenoid 

 fossa ; the scapula has the indication of a spine. The pelvis is 

 stout, attached to four or five vertebrae, converting the latter into 

 a very Mammalian -like sacrum, the position of which lies 

 distinctly in front of the acetabulum. The latter is closed, 

 composed by the three pelvic bones. The pubes and ischia 

 are fused together, leaving only a very small obturator-foramen. 

 The limbs are plantigrade and pentadactyle, very stout ; the 

 humerus and femur have enormous crests. 



Oudenodon, of which several species have been described, is so 

 much like Dicynodon, except for the complete absence of teeth, 

 that it has been suggested that these skulls belong to females of 

 this genus. This view is strengthened by the fact that tusk- 

 like canines exist, or are absent in some of the species which 

 have been described as Cistecephalus, a genus closely allied to 

 Dicynodon. The latter, which, like Oudenodon and Cistecephalus, 

 occurred in Africa, extended also into India, D. orientalis having 

 been found in the Paiichet formation of Bengal, of transitional 

 age between the Permian and Triassic epochs. Oudenodon 

 rugosus, on the other hand, has been described from the Ural. 



Gordonia and Geikia, of the New Red Sandstone of Elgin, are 

 known from their skulls only, but these are so well preserved 

 that there is no doubt about their close relationship to the 

 typical South African Dicynodontia. The skull of Gordonia is 

 about 7 inches long and 4 inches high. The canines (Fig. 54, D, 

 p. 280) are reduced to short, but thick, conical tusks. The most 



