hyomandibular branch VII, 

 laterohyal 



.epihyal 



symplectic. 



ray bar blastema 



percle 



interhyal 



Figure 5-10. Development of the hyomondibulc of the salmon from 

 epihyal and laterohyal blastemas. 



Although the palaeoniscoids had dechned in numbers by 

 the beginning of the Triassic, several genera are well known. 

 These compare well with the earlier genera in superficial 

 detail. As a type for the palaeoniscoids, the species of the 

 Triassic genus Pteronisculus will be used (Figures 5-1 1, 5-12). 



In summary, the paiaeoniscoid type had a complement 

 of dermal bones similar to that already described for the 

 teleost or osteolepid crossopterygian. The primary difFer- 



temporal canal postspiracular 



intertemporal \ 



postorbital 

 supraorbital canal 

 sclerotic ring 



posttemporal 



supracleithrum 



postcleithrum 



internasal 



anterior nasal opening 



nasal. 



anterior medial gular 



dentosplenial 

 coronoids 



parietal 

 supro-postorbitoi 



intertemporal 

 suprotemporotabular. 

 postporieta 

 extrascapulor series 



prearticulor 



bronchiostegal ray ^ . 



^ ' posttemporal. 



rticular area 



Meckel's cartilage 

 angular ^_^_^ metopterygoid area 



A_quadrate area 

 quadratojugal 



internasal I \ lacrimal 

 lateral rostral 

 premaxilla 



angular 



Figure 5-1 1 . Head skeleton of Pferoniscvlvs. A, lateral view of head and pectoral girdle; B, cranial 

 roof; C, anterior view of snout; D, palatal view with palotoquadrate of left side (to right) removed; 

 E, lateral view of suspensorium, palotoquadrate, and lower jaw; ?, medial view of right palate- 

 quadrate complex; G, medial view of mandible. (After Nielson, 1942) 



GNATHOSTOME FISHES • 113 



