THE SKULL OF REPTILES 



29 



or precoronoid. Primitively (Fig. 18) it often bore teeth, as in many 

 temnospondyls, but no such teeth are known in later reptiles. 



The surangular (sa), always present in reptiles, though sometimes 

 indistinguishably fused with the articular, forms the upper margin 

 of the mandible back of the coronoid, and the outer margin of the 



Fig. 15. Trimerorhachis insignis. Temnospondyl mandible: A, right ramus 

 from below; B, the same from above. 



MeckeHan orifice (Figs. 15-18). In some it may take part in the 

 articular surface for the quadrate. 



The angular {an), on the inferior border posteriorly, articulating 

 with the dentary in front, the prearticular, articular, and surangular 

 behind, and extending to the hind angle of the jaw, is always present 

 (Figs. 15-18). In the crocodiles (Fig. 69 c, d) it helps form the inner 

 border of the Meckelian orifice. 



