14 



Fishery Bulletin 90(1). 1992 



'^"•iirairi'^i-itlliiillftlM'i"'^- 



B 



Figure I 



Species of Gr animator cynus. (A) G. bilineatus (from Evermann and Seale 1907. fig. 3, holotype oi Nesogrammus piersoni, 372mm 

 FL, Philippine Is.); (B) G. bicarinatus (from McCulloch, 1915, p. 1, fig. 1, 925 mm FL, New South Wales, Australia). 



Part 1: Comparative morphology 



Morphological characters useful for distinguishing be- 

 tween species of Grammatorcynus and for evaluating 

 phylogenetic relationships of the genus are divided into 

 six categories: lateral line, color pattern, morphometry, 

 meristic characters, soft anatomy, and osteology. 



Lateral line 



The genus Grammatorcynus differs from all other 

 genera of Scombridae in having two lateral lines, hence 

 their common name, double-lined mackerels. The 

 dorsal-most lateral line is slightly convex, originates 

 near the dorsal portion of the opercle, and continues 

 posteriorly until it converges with the second lateral 

 line, just anterior to the median caudal keel. The sec- 



ond lateral line originates from the first at a point 

 below the first four spines of the dorsal fin. It starts 

 ventrally, running under, or just posterior to, the pec- 

 toral fin, and abruptly turns into a concave line that 

 continues posteriorly until meeting the dorsal lateral 

 line (Fig. 1). The function of this additional lateral line 

 is unknown. The characteristic two lateral lines are 

 discernible in specimens as small as 56.9mm SL 

 (Nishikawa 1979:133). Anomalies in the pattern of the 

 lateral lines are occasionally found, but none appear 

 to be species specific (Fig. 2; Silas 1963: fig. 3). 



Color pattern 



Dark spots are usually found on the ventral portion of 

 G. bicarinatus (Fig. IB). The spots are smaller than 

 the pupil, originate near the ventral border of the oper- 



