trabecule 



irbilol cartilage 



otic process of 

 quadrate cartilage 

 pila ontotica 



B 



quadrate cartilage 



bosicopsular fenestra 

 lateral woll of otic capsule/' 

 notochord 



quadrate corttlagt 



facial foramen 



otic capsuli 

 vestibular fontonelle 



D 



epibranchials 

 cerotobronchiols l-lll 



superficial ophthalmic VII 

 trabeculo communis 



ascending process 

 pineal body, 

 orbital cartilage. 



trabecule 



pharyngohyol 



epibronchial I 

 cerato branchial I 



cerotohyal 



Meckel's cartilage 



foramen epiphoniale 

 trabecular cornua 



lamino 



orbitonasolis 



sphenethmoid commissure 

 laterohya 

 quadrate, 

 epihyal- 



hyomandibulo 

 branch VII 



notochord 



ateral head vein 

 orbital artery 



procartiloginous 

 palatoquadrate 



otic process of quadrate cartilage 

 superficial ophthalmic VII, ^2.2 

 ascending process 



phenethmoid 

 commissure 



hyomandibulo 



.occipital arch 



Meckel's cartilage' 



epiphyseal tectum 



hypophyseal fenestra 



lamina tronsversalis anterior 



orbitonasol lamina 

 pituitary vein 



synotic tectum 

 otic capsule 



basihyol 



hypohyal 

 Meckel's cartilage 



lateral head vein 



Figure 4-39. Development of chondrocrcnium of Neocerofoc/us. A, B, dorsal and lateral views of 

 head skeleton of 1 2-mm larva (After DeBeer, 1937); C, ventral view of head skeleton of 1 1 .5-mm 

 larva (after Bertmar, 1959); D, lateral view of head skeleton of 12.6-mm larva (after Bertmar); 

 E, dorsal view of head skeleton of 20-mm larva with part of left side cut away (after DeBeer); F, lateral 

 view of head skeleton of 27-mm larva (after Holmgren and Stensio, I 936); G, sectional view of head 

 skeleton, looking forward, showing relationships of parts of hyoid arch to other structures (after 

 Bertmar, 1959, and Goodrich, 1930) 



suprahyal lies between the palatine and hyomandibular 

 branches of the facial nerve and its suprahyal process extends 

 upward to contact and fuse with the otic capsule lateral to 

 the head vein. Thus the lateral commissure is formed from 

 the pharyngosuprahyal. 



Meanwhile an epihyal chondrification has appeared above 

 the symplectic, and this center is joined above by a latero- 

 hyal center of subepidermal mesenchyme. The latter element 

 expands, chondrifies, and fuses with the epihyal to form the 



hyomandibula of the adult, which lies behind the hyoman- 

 dibular branch of the facial nerve. The symplectic may fuse 

 with the quadrate, lie in the ligament joining the quadrate 

 and ceratohyal, or disappear. 



The hyomandibula is better developed in the crossopte- 

 rygian, where it articulates with the lateral commissure by 

 two heads, above and below the level of the head vein. This 

 is the same situation as in the actinopterygian. 



Although the stapes of the tetrapod has been compared 



CHOANATE FISHES 



103 



