30 



Fishery Bulletin 90(1). 1992 



23-28% of length) and wider (S. maculatus width 

 41-42% of length) entopterygoids. The entopterygoid 

 of Acanthocybium (30-35%) is slightly narrower than 

 that of Grammatorcynus (35-41%). 



Metapterygoid The metapterygoid is a flat, 

 quadrangular or somewhat triangular bone (Fig. 18). 

 The posterodorsal margin of this bone is deeply 

 grooved to receive the hyomandibula. The dorsal por- 

 tion is strongly ankylosed to the lamellar region of the 

 hyomandibula. The ventroposterior margin abuts the 

 lowermost portion of the symplectic process of the 

 hyomandibula, but does not touch the hyomandibula. 

 There is a relatively long slit beween the two bones 

 through which the hyoidean artery passes (Allis 1903). 

 The ventral border is divided into two portions: the 

 horizontal portion in contact with the quadrate and the 

 anterior oblique portion ankylosed to the ectopterygoid. 

 On the mesial surface, the metapterygoid has a 

 triangular-shaped area that forms an interdigitating 

 articulation with the upper arm of the ectopterygoid. 

 The posteroventral margin of the metapterygoid articu- 

 lates with the dorsal end of the symplectic in Gram- 

 matorcynus (Fig. 18c) and Acanthocybium (Fig. 18b), 

 but does not do so in most species of Scomberomorus 

 (Fig. 18a). The posterior, horizontal part of the ven- 

 tral border is shorter than the anterior oblique part in 

 Grammatorcynus (anterior part 132-181% of posterior 

 part) and Acanthocybium (188-218%); however, in 

 Scomberomorus the posterior part is longer than the 

 anterior part (anterior part 39-86% of posterior part). 



Hyoid arch The hyoid arch is composed of the 

 hyomandibula, symplectic, quadrate, hyoid complex 

 (hypohyals, ceratohyal, epihyal, interhyal, and the 

 seven branchiostegal rays), and two median unpaired 

 bones, the glossohyal and urohyal. 



Hyomandibula The hyomandibula is an in- 

 verted L-shaped bone (Fig. 18) connecting the man- 

 dibular suspensorium and opercular bones to the 

 neurocranium. Dorsally, there are three prominent con- 

 dyles. The long dorsal condyle forms the base of the 

 L and fits into the fossa at the junction of the pterotic 

 and sphenotic bones. The anterior condyle articulates 

 with the ventral fossa of the pterotic, and the lateral 

 process is attached to the inside of the opercle. 

 Anterolaterally, the hyomandibula is drawn out into a 

 lamellar region that joins the metapterygoid. Postero- 

 laterally, it has a long articulation with the preopercle. 

 Ventrally, the hyomandibula has a long symplectic pro- 

 cess; at the posterodorsal corner there is a small, 

 sometimes almost indistinct spine. A strong vertical 

 ridge extends from the ventral margin to just below 

 the dorsal border, where it then curves anteriorly to 

 confluence with the anterior condyle. The areas lying 

 anterior and posterior to this ridge are grooved for 

 articulation with the metapterygoid and preopercle. 



respectively; in situ, only the ridge and a portion of the 

 upper broader surface are visible exteriorly. The upper 

 surface of the symplectic is connected to the ventral 

 border of the hyomandibula by way of a cartilage, best 

 developed in Acanthocybium. There is one deep fossa 

 on the inner surface of the hyomandibula in Gramma- 

 torcynus (Fig. 18c) and Scomberomorus (Fig. 18a); 

 there are two such fossae m Acanthocybium (Fig. 18b). 

 The posterodorsal spine, which is quite small in 

 Grammatorcynus and in most species of Scomberomo- 

 rus, is best developed in Acanthocybium, S. commer- 

 son (Devaraj 1977), and S. queenslandicus. The max- 

 imum width (tip of anterior condyle to outer margin 

 of posterior condyle) of the hyomandibula is least 

 relative to the total length (ventral tip to dorsal margin 

 of dorsal condyle) in Grammatorcynus (width 34-39% 

 of length) and S. multiradiatus (36-39%). The hyoman- 

 dibula is widest, relative to length in S. sinensis 

 (45-52%). Acanthocybium and the other species of 

 Scomberomorus fall between these two extremes 

 (39-47%). 



Symplectic The symplectic is a small bone that 

 fits into a groove on the inner surface of the quadrate 

 (Fig. 18). In Grammatorcynus the symplectic is slightly 

 wider than it is in Scomberomorus; however, the groove 

 into which the symplectic fits is narrower in Gramma- 

 torcynus than in Scomberomorus, so that the symplec- 

 tic nearly fills the groove in Grammatorcynus and does 

 not fill the groove in Scomberomoms (Fig. 18a). The 

 symplectic is greatly expanded at its dorsal end in 

 Acanthocybium (Fig. 18b). The symplectics in Gram- 

 matorcynus and Acanthocybium extend well beyond 

 the dorsal margin and even beyond the dorsal end of 

 the posterior process of the quadrate to make contact 

 with the metapterygoids, making them much longer 

 than the symplectics in most species oi Scomberomo-r-us. 

 The symplectic of G. bilineatus (Fig. 19a) is longer than 

 that of G. bicarinatus (Fig. 19b). 



Quadrate The lower jaw is suspended from the 

 cranium by means of the articulating facet of the ven- 

 tral surface of the triangular quadrate (Fig. 18). The 

 broad dorsal margin of the quadrate abuts the ventral 

 border of the metapterygoid. There is a strong process 

 on the posterior margin of the quadrate that is attached 

 along the lower anterior arm of the preopercle. This 

 process is quite long in G. bilineatus (its length mea- 

 sured from the ventral facet to the tip of the process 

 is 134-145% of the distance from the ventral facet to 

 the dorsal margin; Fig. 19a) and Acanthocybium, but 

 shorter in G. bicarinatus (122-125%, Fig. 19b) and 

 most species of Scomberomorus. 



Hyoid complex This complex includes the two 

 hypohyals (basihyal of Mago Leccia 1958), ceratohyal, 

 epihyal, and interhyal bones, and the seven branchio- 

 stegal rays (Collette and Russo 1985b: fig. 29). The 



