COLLETTE and RUSSO: SPANISH MACKERELS 



a 



FIGURE 28. — Left entopterygoids in dorsal view. a. Scomberomorus commerson, New South Wales, 1,155 mm FL, 1 x . b. Scomber- 

 omorus sinensis, Hong Kong, 677 mm FL, 2 x . c. Acanthocybium solandri, Indian Ocean, 943 mm FL, 2 x . d. Grammatorcynus 

 bilineatus, Marshall Is., 424 mm FL, 2.5 x . 



Fig. 28b), maculatus (41-42%), and concolor 

 (40-42% ). Acanthocybium (Fig. 28c), Grammator- 

 cynus (Fig. 28d), and the other 13 species of Scom- 

 beromorus are intermediate in width (30-40%). 



Metapterygoid. — The metapterygoid (Fig. 27) 

 is a flat, quadrangular or somewhat triangular 

 bone. The posterodorsal margin of this bone is 

 deeply grooved to receive the hyomandibula. The 

 dorsal portion is strongly ankylosed to the lamel- 

 lar region of the hyomandibula. The ventroposte- 

 rior margin abuts the lowermost portion of the 

 symplectic process of the hyomandibula, but does 

 not touch the hyomandibula. There is a relatively 

 long slit between the two bones, through which 

 the hyoidean artery passes (Allis 1903). The ven- 

 tral border is divided into two portions, the hori- 

 zontal portion in contact with the quadrate and 

 the anterior oblique portion ankylosed to the 

 ectopterygoid. On the mesial surface, the meta- 

 pterygoid possesses a triangular-shaped area 

 which forms an interdigitating articulation with 

 the upper arm of the ectopterygoid. The postero- 

 ventral margin of the metapterygoid articulates 



with the dorsal end of the symplectic in Acantho- 

 cybium and Grammatorcynus (Fig. 27b, c), but 

 not in most species of Scomberomorus (Fig. 27a). 

 The posterior horizontal part of the ventral bor- 

 der is longer than the anterior oblique part in 

 Scomberomorus (anterior part 39-86% of poste- 

 rior part), but vice versa in Acanthocybium and 

 Grammatorcynus (anterior part 132-218% of pos- 

 terior part). 



The anterior part of the ventral margin is 

 relatively longer in S. multiradiatus (77-78% of 

 posterior part) and S. maculatus (65-86%), and 

 relatively shorter in S. plurilineatus (41-45%) 

 and S. regalis (39-50%). Devaraj (1977) reported 

 differences in the shape of the anterior free border 

 of the metapterygoid, as convex, nearly straight, 

 or concave. We have found similar tendencies but 

 it is difficult to place the species of Scomberomo- 

 rus in specific categories. 



HYOID ARCH.— The hyoid arch is the chain of 

 bones that connect the lower jaw and the opercu- 

 lar apparatus with the skull. The arch is com- 

 posed of the hyomandibula, symplectic, quadrate, 



583 



