Collette and Gillis Osteological differences between two species of Grammatorcynus 



19 



SPHENOTIC 



PTEROTIC 



FRONTAL 



NASAL 



INTERCALAR 



EPIOTIC 



EXOCCIPITAL 



VOMER 



ETHMOID 

 _ LATERAL ETHMOID 



a 



FIRST VERTEBRA 

 SUPRAOCCIPITAL 



PARIETAL 



Figure 6 



Dorsal view of skulls in Grammatorcynus. (a) G. bilirwatiis, Scott Reef, Timor Sea, 453mm FL; (b) G. bicarinatus. 

 Western Australia, Exmouth Gulf, 765 mm FL. 



extends almost to the ethmoid in G. bilineatus. The 

 ridge curves around the anterior end of the space and 

 ends distinctly more posteriorly in G. bicarinatus. This 

 difference cannot be seen in the ventral view of the 

 skulls (Fig. 8) because the median part of the opening 

 is obscured by the parasphenoid, so a separate outline 



figure has been made (Fig. 9). 



Pterosphenoid The pterosphenoids (alisphe- 

 noids) form the posterodorsal margin of the orbit. They 

 serve as the base for the median basisphenoid, and abut 

 the prootics posteriorly and the frontals and sphenotics 

 laterally. 



