SKULL REPTILES 



167 



choana? separated by the vomers. The more posterior nares, large antorbital 

 vacuities, a short basisphenoid, and the approach of the pterygoids to the 

 middle line suggest Dinosaurs. 



PTEROSAURIA.— The skulls (fig. 180) of these extinct flying reptiles are 

 decidedly bird-like in shape, in the angle at which they are borne on the vertebral 

 column and the extent to which sutures are obliterated. The lack of teeth in 



Fig. 179. — Dorsal, ventral and basal views of hinder part of cranium of Mystrio- 

 suchus (McGregor, '06). bo, basioccipital; bs, basisphenoid; eo, exoccipital; /, frontal; 

 /, lacrimal; m, maxilla; w, nasal; 00, opisthotic; p, parietal; pi, palatine; po, postorbital; 

 pof, postfrontal; prf, prefrontal; pa, parasphenoid; pt, pterygoid; q, quadrate; qj, 

 quadratojugal; so, supraoccipital; sq, squamosal; I, transversum; s, zygomatic. 



the elongate beak of some species increase the resemblance; but fhere are many 

 differences. Both temporal fossae are present, the lower a narrow cleft behind 

 the orbit, the quadrate forming its posterior wall. The superior fossa is far 

 back on the cranium. The base of the skull looks obliquely down and back, 

 and the skull is nearly at right angles with the neck. There is no parietal 



Fig. 180. — Skull of pterodactyl {Scaphognalhus, Zittel. '90). /, frontal; nix, maxilla; 

 p, premaxilla; q, quadrate; 2, zygomatic. 



foramen and the small parietals sometimes reached the anterior border of the 

 orbit. The fused frontals form most of the cranial roof, the elongate maxiUie 

 most of the beak. The large antorbital vacuity is confluent with the naris in 

 some genera. The orbits, sometimes with sclerotics, are separated from the 



