the quadrate to the ear capsule. A blastema of the pterygoid 

 process extends forward from the quadrate region to the tip 

 of the orbitonasal process but later disappears. 



The origin of the hyomandibula o{ Neoceratodus has been 

 fully described. There are several centers of chondrification 

 involved in the upper region of the hyoid arch. The first to 

 chondrify is the symplectic. This is followed by the pharyn- 



gosuprahyal, the epihyal, and the laterohyal, which is a 

 new development in the dermal tissue. The pharyngo- 

 suprahyal at first is continuous with the blastema of the 

 remainder of the arch. It then joins the basal plate of the 

 cranium medioventral to the lateral head vein. Following 

 this, connection is lost laterally— specifically it detaches from 

 the epihyal condensation. The lateral end of the pharyngo- 



interparietal 



extrascapular 



anterior splenial 



preopei'cular series 

 splenoangular 



nasal openings 

 (dashed lines) \^- 



pterygoi 



quadrate 



internasal 



labial cartilage 



Sx_lacrimal 

 ^jugoj 

 A—postorbital 



ntertemporal 



supratemporotabular 

 opercle 



extrascapular 



spinoccipital foramina 

 V,VII exoccipital 



carotid canal 

 ophthalmic artery 



efferent pseudobranchlal 

 artery 



VII 

 ;_carotid canal 



hyomandibula 



ateral head vein 

 (cranioquadrote fissure 

 opercle 



prearticulor with' 

 teeth 



bosihyal hypohyal 



ceratohyal 



notochord 

 subopercle 

 porasphenoid 



Figure 4-38. Head skeleton of Neocerofodus. A, lateral view of head skeleton; B, lateral view of 

 cranium with opercular and cheek bones removed; C, dorsal view of skull; D, palatal view of skull; 

 E, medial view of right half of head. (In part after Holmgren and Pehrson, 1936) 



102 . HEAD SKELETON OF OTHER TETRAPODS AND CHOANATES 



