40 



Fishery Bulletin 90(1). 1992 



pectoral fin rays, similar to Acanthocybium (22-26). 

 Scombermorus shows greater variation (19-26) in this 

 character and in most species averages less than either 

 Grammatorcynus or Acanthocybium. There is a slight 

 difference in number of pectoral fin rays between the 

 species of Grammatorcynus: G. bilineatu^ has a range 

 of 22-26, mode 25, x 24.4; G. bicarinatus 21-24, 

 mode 24, x 23.2 (Table 6). 



First postcleithrum The posterior projecting plate 

 of the cleithrum has its posterior end attached to the 

 first postcleithrum which connects ventrally to the 

 second postcleithrum. The lamellar first postcleithrum 

 has a narrower upper end and a wider, rounded lower 

 margin (Fig. 23). The upper end is concave in Gram- 

 matorcynus (Fig. 23c-d) and pointed in both Scombero- 

 morus (Fig. 23a) and Acanthocybium (Fig. 23b). The 

 width of the postcleithrum varies from 46 to 62% of 

 the length of the bone in Grammatorcynus. It is nar- 

 rower in G. bicarinatus (width 46-52% of length, Fig. 

 23d) than in G. bilineatus (55-62%, Fig. 23c). In Acan- 

 thocybium (47-48%, Fig. 23b) the width is similar to 

 that of G. bicarinatus. Species of Scomberomorus (Fig. 

 23a) have narrower postcleithra (24-41%) than the 

 other two genera. 



Second postcleithrum The second postcleithrum 

 is broad and lamellar at the upper part with a short 

 pointed ascending process and a long styliform 

 descending process. Grammatorcynus (Fig. 24d) dif- 

 fers strikingly from Acanthocybium (Fig. 24c) and 

 Scomberomorus (Fig. 24a-b) in having a distinct pro- 

 cess extending anteriorly from the broad lamellar por- 

 tion of the bone. The long descending process is so thin 

 in most specimens that an accurate measurement of 

 its length is nearly impossible because some portion of 

 it usually breaks off. No differences were detected in 

 this bone between the two species of Grammatorcynus. 



Pelvic girdle The pelvic fin rays (1, 5) attach directly 

 to the paired basipterygia that make up the pelvic gir- 

 dle. The bones are united along the midline and are im- 

 bedded in the ventral abdominal wall, free from con- 

 tact with other bones. Each basipterygium is compos- 

 ed of three main parts: a wide anterodorsal plate, a 

 thin, flat anterior process, and a strong posterior 

 process. 



To compare the pelvic girdles, the lengths of the 

 three parts were measured from their bases to their 

 tips. Grammatorcynus has the longest anterior process 

 (46-51% of the length of the anterodorsal plate. Fig. 

 25d), Acanthocybium has the next longest (35-47%, 

 Fig. 25c), and Scomberomorus the shortest (15-52%, 

 Fig. 25a-b). Grammatorcynus (29-33%, Fig. 25d) and 

 Acanthocybium (30-39%, Fig. 25c) have shorter pos- 

 terior processes than the species of Scomberomorus 



a 



Figure 23 



Left first postcleithra in lateral view, (a) Scomberomarus 

 sinensis, Hong Kong, 677 mm FL, 1 x ; (b) Acanthocybium 

 solandri, Revillagigedos Is., 1068mm FL, 1 x ; (c) Gram- 

 matocynus bilineatus, Queensland, 521mm FL, 2x; (d) 

 G. bicarinatus, Queensland, 563mm FL. 



(20-90%, Fig. 25a-b). 



Grammatorcynus, some individuals of Acantho- 

 cybium, and several species of Scomberomorus have 

 longer anterior than posterior processes. The lengths 

 of the anterior process as a percentage of the posterior 

 process are: Grammatorcynus (154-158%), Acantho- 

 cybium (91-156%), and Scomberomorus species 

 (42-121%). 



