28 



Fishery Bulletin 90(1), 1992 



a 



Figure 16 



Left palatines in lateral view, slightly rotated to better show tooth patches, (a) Scomberomorus semifaseiatus. New Guinea. 

 740mm FL, 2x; (b) Scomberomorus commerson, New South Wales, 1155mm FL, Ix; (c) Acanthocybium solandri. Miami, 

 PL, 1403mm FL, Ix; (d) Grammatorcynus bilineatus. Timor Sea, 453mm FL, 2x. 



ventral process as long or longer than the dorsal pro- 

 cess. All other species of Scomberomorus (Fig. 15a) 

 have ventral processes that are relatively shorter. 



Retroarticular (Fig. 15) The retroarticular bone 

 (frequently called the angular) is rhomboid and at- 

 tached firmly, but not fused, to the posteroventral 

 margin of the angular. No differences were found 

 between the retroarticulars of the species of Gramma- 

 torcynus. 



Palatine arch The palatine arch consists of four 

 pairs of bones in the roof of the mouth: palatine, 

 ectopterygoid, entopterygoid, and metapterygoid. 



Palatine The palatine is forked both posteriorly 

 and anterolaterally (Fig. 16). The dorsal branch of the 

 anterolateral fork is hooked, and its anterior end 

 articulates v/ith a facet on the maxilla, immediately 

 ventral to the nasal. The ventral branch appears almost 

 indistinct in comparison with the longer ventral branch 

 oi Acanthocybium (Fig. 16c) and the even longer ven- 

 tral branch oi Scomberomorus (Fig. 16a-b). In Scom- 

 beromorus, the ventral branch is longer than the dorsal 

 branch, which is not true of Grammatorcynus or 

 Acanthocybium. The distance from the anterior end of 

 the ventral branch to the end of the external branch 

 divided by the distance from the tip of the dorsal hook 

 to the end of the external branch is 118-125% in Gram- 

 matorcynus, 112-121% in Acanthocybium, and only 



87-107% in Scomberomorus. The distance from the tip 

 of the dorsal hook to the tip of the inner branch divided 

 by the distance to the tip of the outer branch is 71-75% 

 in Grammatorcynus, 54-84% in Scomberomorus, and 

 97-99% in Acanthocybium. Hence, Acanthocybium dif- 

 fers from both Grammatorcynus and Scomberomorus 

 in that its posteriorly directed inner branch is almost 

 as long as the outer branch. The tooth patch is short 

 and wide in Grammatorcynus (Fig. 16d), more so in 

 G. bicarinatus (wadth 38-42% of length. Fig. 17b) than 

 in G. bilineatus (width 26-32% of length. Fig. 17a), 

 long and narrow in Acanthocybium., and between the 

 two extremes in Scomberomorus. The teeth are fine in 

 all three genera, but are a little larger in Gramma- 

 torcynus and Acanthocybium than in most species of 

 Scomberomorus. 



Ectopterygoid The ectopterygoid is a T-shaped 

 bone with the top of the T forming its posterior end. 

 It joins with the entopterygoid dorsolaterally, the 

 palatine laterally and anteriorly, and the quadrate and 

 metapterygoid posteriorly (Fig. 18). Dividing the dor- 

 sal distance (from the anterior end of the bone to the 

 tip of the dorsal arm) by the ventral distance (from the 

 anterior end to the tip of the ventral process) results 

 in a number that is greater than 100% in Gramma- 

 torcynus (107-116%, Fig. 18c) and Acanthocybium 

 (103-109%, Fig. 18b), but only 85-100% in Scombero- 



