26 



Fishery Bulletin 90(1), 1992 



Figure 13 



Supramaxillae in lateral view in Gramma- 

 torcyniis. (a) G. bilineatus. Western Aus- 

 tralia, 460 mm FL; (b) G. bicarinatus, 

 Australia, 625 mm FL. 



concavity facing the inner wall of the premaxilla. Im- 

 mediately posterior to the head is a shallow depression 

 that receives the anterior articulating process of the 

 palatine. The shank of the maxilla is narrow and 

 somewhat flattened. It remains at a relatively constant 

 height along its entire length, unlike the shank of 

 Scomberomorus (Fig. 12a) in which the posterior end 

 of the shank expands into a flat plate. The posterior 

 end is distinctly thinner than the middle of the shank 

 in Acanthocyhium (Fig. 12b). 



The head of the maxilla is longer (25-29% of total 

 maxilla length) in Grammatorcynus than in any species 

 oi Scomberomorus (18-25%) but shorter than in Acan- 

 thocyhium (33%, Fig. 12b). 



The height of the posterior end of the shank, relative 

 to the total length of the maxilla, is less in G. bicari- 

 natus (6-8%, Fig. 12d) than in G. bilineatus (8-11%, 

 Fig. 12c). Grammatorcynus bilineatus is similar to 

 those species of Scomberomorus that have the least 

 well-developed (lowest) posterior expansions: S. multi- 

 radiatus (8-9%) and S. sinensis (9-11%). Other species 

 of Scomberomorus, such asS. munroi (Fig. 12a), have 

 larger posterior expansions (11-15%). 



Supramaxilla The supramaxilla (Fig. 13) covers 

 the posterior end of the maxilla. It is a small, flat bone 

 that is expanded posterodorsally. The expansion is 

 much more pronounced in G. bicarinatus (59-76% of 

 bone length. Fig. 13b) than in G. bilineatus (35-42%, 

 Fig. 13a). 



Figure 14 



Left dentaries in lateral view, (a) Scomberoinorus semi- 

 fasciatiis, Port Moresby, New Guinea, 510mm FL, 2x; (b) 

 Acanthocybium solandri, Miami, FL, 1403mni FL, Ix; (c) 

 Grammatorcynus bilineatus, Marshall Is., 424 mm FL; (d) 

 G. bicarinatus, Western Australia, 765mm FL, Ix. 



Dentary The dentary (Fig. 14) is laterally flat- 

 tened and bears a single row of 12-32 long, thin teeth 

 on the dorsal margin. Posteriorly, the dentary has two 

 arms of the same relative width (the ventral arm may 

 be slightly narrower), un\\ke Scomberomorus (Fig. 14a) 

 and Acanthocybium (Fig. 14b) where the ventral arm 



