PTEROSAURIA. 



389 



sternum has a keel and tliere is no clavicle. The skull is rounded and 

 bird-hke. The occipital condyle is single and on the base of the skull 

 Ths cranial bones ankylose eai-ly as in birds, the orbits are large and with 



Fig. 215.— Dimorphodon macronyx restoration y.\, L. Lias (after Owen, from Woodward) 

 a antorbital fossa ; n external nares ; o orbit. 



sclerotic plates, and there is a wide antorbital fossa as in Aves and Dino- 

 eauria. There is a postfrontal, and both upper and lower temporal arcades 

 are present. Teeth are frequently present (on the margins of the jaws only). 



