FISHERY BULLETIN: VOL. 82, NO. 4 



hyoid complex (hypohyal, ceratohyal, epihyal, 

 interhyal, and the seven branchiostegal rays), 

 and two median unpaired bones, the glossohyal 

 and urohyal. 



Hyomandibula. — The hyomandibula (Fig. 27) 

 is an inverted L-shaped bone that connects the 

 mandibular suspensorium and opercular bones to 

 the neurocranium. There are three prominent 

 condyles on the dorsal end of the hyomandibula. 

 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 con- 

 dyle articulates with the ventral fossa of the 

 pterotic and the lateral process is attached to the 

 inside of the opercle. Anterolateral^, the hyo- 

 mandibula is drawn out into a lamellar region 

 that joins the metapterygoid; posterolateral^, it 

 has a long articulation with the preopercle. Ven- 

 trally, the hyomandibula has a long symplectic 

 process; at the posterodorsal corner there is a 

 small spine. A strong vertical ridge extends from 

 the ventral margin to a little below the dorsal 

 border, thence it curves anteriorly to confluence 

 with the anterior condyle. The portions lying 

 anterior and posterior to this ridge are grooved 

 for articulation with the metapterygoid and pre- 

 opercle 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 hyoman- 

 dibula by way of a cartilage which is especially 

 well developed in Acanthocybium. There are two 

 deep fossae on the inner surface of the hyoman- 

 dibula of Acanthocybium but only one in Scom- 

 beromorus and Gr animator cynus. 



The posterodorsal spine is best developed in 

 Acanthocybium (Fig. 27b) and S. commerson, as 

 pointed out by Devaraj (1977). This spine is also 

 well developed in S. queenslandicus and is pres- 

 ent but small in the other 16 species of Scom- 

 beromorus (e.g., S. semifasciatus , Fig. 27a). No 

 spine is present in Grammatorcynus (Fig. 27c). 

 The total length of the hyomandibula (ventral tip 

 to dorsal margin of dorsal condyle) is greater 

 relative to maximum width (tip of anterior con- 

 dyle to outer margin of posterior condyle) in 

 Grammatorcynus (width 35-36% of length) and 

 S. multiradiatus (36-39%). The hyomandibula is 

 shortest relative to width in S. sinensis (45-52%). 

 Acanthocybium (41-44%) is similar to the major- 

 ity of species of Scomberomorus (39-47%). 



Symplectic. — The symplectic is a small bone 

 584 



that fits into a groove on the inner surface of the 

 quadrate (Fig. 27). The symplectic is very narrow 

 in Scomberomorus, not filling the groove in the 

 quadrate (Fig. 27a). It is slightly wider in Gram- 

 matorcynus but the groove is narrower, the sym- 

 plectic more nearly filling the groove (Fig. 27c). 

 The symplectic is greatly expanded at its dorsal 

 end in Acanthocybium (Fig. 27b). In most species 

 of Scomberomorus , the symplectic, like the poste- 

 rior process of the quadrate, extends only a slight 

 distance beyond the dorsal margin of the quad- 

 rate. The symplectic is slightly longer than the 

 posterior process in a species with a short process 

 (e.g., S. multiradiatus) and in one with a rela- 

 tively long process (e.g., S. sinensis). No bony 

 contact is present between the dorsal end of the 

 symplectic and either the metapterygoid or the 

 hyomandibula in most species of Scomberomo- 

 rus. The metapterygoid is in slight contact with 

 the symplectic in S. sinensis and S. koreanus. 

 Both Grammatorcynus and Acanthocybium have 

 much longer symplectics, extending well beyond 

 the dorsal margin of the quadrate and even 

 beyond the dorsal end of the posterior process 

 to make firm contact with the metapterygoids. 

 Devaraj (1977: fig. 11) illustrated the symplectics 

 by themselves for the four Indian species {korea- 

 nus, guttatus, lineolatus, and commerson) and 

 Acanthocybium. 



Quadrate. — The lower jaw is suspended from 

 the cranium by means of the articulating facet of 

 the ventral surface of the triangular quadrate. 

 The broad dorsal margin of the quadrate abuts 

 the ventral border of the metapterygoid (Fig. 27). 

 The mesial surface of the quadrate bears a deep 

 groove which accepts the symplectic. There is a 

 strong process on the posterior margin of the 

 quadrate that is attached along the lower ante- 

 rior arm of the preopercle. The process is relative- 

 ly short in Scomberomorus, extending only a 

 short distance beyond the dorsal margin of the 

 quadrate in most species (e.g., S. semifasciatus, 

 Fig. 27a). The process is shortest in S. multiradia- 

 tus, not reaching the dorsal margin. The process 

 is longest in S. commerson, S. lineolatus, and S. 

 sinensis, but it is still shorter in these three 

 species than in Acanthocybium (Fig. 27b) and 

 Grammatorcynus (Fig. 27c). An attempt was 

 made to quantify this by measuring from the 

 inside of the articular facet to the tip of the dorsal 

 process and to the tip of the anterior margin of 

 the quadrate. The short process in S. multiradia- 

 tus is shown by the distance to the anterior 



