THE SKULL OF REPTILES 77 



The Skull of the Pseudosuchia 



(Fig. 65 a-e) 



The skull of the typical Pseudosuchia is very much like that of the 

 Pelycosimia (Fig. 64), in structure. All the bones of the skull roof 

 are present except the dermosupraoccipital, tabular, and supra- 

 temporal; the lacrimal is small; there is no parietal foramen; and the 

 palate bones have the primitive relations. Other forms, however, 

 referred to this group provisionally, have both the dermosupra- 

 occipital and tabular {Youngina, Fig. 64 c), and teeth on the pre- 

 vomers and pterygoids (Proterosuchus). The upper and lateral 

 temporal openings, a large antorbital vacuity and one in the man- 

 dible, are like those of the Parasuchia. The antorbital foramen is 

 large, as are also the orbits. The supra temporal foramen is large 

 and never posterior in position. 



The Skull of the Pelycosimia 



(Fig. 64) 



The skull of the Pelycosimia differs from that of the Phytosauria 

 chiefly in the position of the external and internal nostrils near the 

 extremity of the face, and at a considerable distance in front both of 

 the orbits and antorbital openings. The face is short in front of the 

 nostrils. There is also no respiratory channel back of the internal 

 nostrils, so characteristic of the phytosaurs. The skull is markedly 

 carnivorous in type. 



