FISHERY BULLETIN: VOL. 73, NO. 3 



Figure 41.-Right quadrates of six species of Sardini, internal 

 view to show groove for symplectic. a. Cybiosarda elegans, New 

 South Wales, 355 mm FL. b. Orcynopsis unicolor, Tunisia, 645 

 mm FL. c. Sarda sarda, Florida, 333 mm FL. d. Sarda australis, 

 New South Wales, 495 mm FL. e. Gymnosarda unicolor, Truk 

 Islands, 696 mm FL. f. Allothunnus fallai, California, 680 mm 

 FL. 



serrated suture that is most prominent in Gym- 

 nosarda (Figure 42e). There is a depression on the 

 outer surface at the posterior half of the suture in 

 all bonitos, as in Thunnus. Internally, a lateral 

 process at the anterodorsal end forms a symphysis 

 with the glossohyal, urohyal, basibranchial, and 

 the process of the hypohyal from the opposite side. 

 The ceratohyal is a long flat bone, broader at the 

 posterior end and with an anteroventral projec- 

 tion that articulates with the posteroventral notch 

 of the hypohyal. The middle portion of the cera- 

 tohyal is concave dorsally in all bonitos. There are 

 three notches along the ventral margin where the 

 anterior three branchiostegal rays attach. Bonitos 

 have no notch at the site of attachment of the 

 fourth branchiostegal ray. All bonitos have an 



elliptical ceratohyal window (Nakamura and Mori 

 1966, fig. 6), except for Sarda orientalis which has 

 only a trace of a depression at the appropriate site 

 (Figure 42d). A deep groove extends along the 

 upper third of the ceratohyal from the depression 

 of the hypohyal to the middle of the epihyal in 

 Gymnosarda, but there is only a slight trace of this 

 groove in the other bonitos. 



The epihyal is a triangular bone which in- 

 terlocks medially with the ceratohyal. This serrat- 

 ed interlocking suture is limited to the inner sur- 

 face of the bone in Cybiosarda, Orcynopsis, and 

 Sarda (Figure 42 a-d); there are only cartilaginous 

 connections between these two bones on the outer 

 surface, as in Thunnus (de Sylva 1955, fig. 36). 

 Gymnosarda and Allothunnus also have well- 

 developed interlocking sutures on the outer sur- 

 face (Figure 42 e, f). The epihyal bears a small 

 condyle on its posterior end that articulates with 

 the inner surface of the interopercle. The fifth to 

 seventh branchiostegal rays are attached to the 

 outer surface of the ventral margin of the epihyal. 

 The fifth branchiostegal is at the junction of the 

 epihyal and ceratohyal in Gymnosarda and is a 

 short distance behind the junction in other boni- 

 tos. 



The interhyal is a small bone with an expanded 

 ventral end that is attached to the epihyal dorsal to 

 the epihyal condyle. The interhyal is attached, 

 with connective tissue, to the symphysis of the 

 hyomandibula, quadrate, symplectic, meta- 

 pterygoid, and preopercle. The interhyal also ar- 

 ticulates above the interopercular fossa 

 posteriorly. 



Glossohyal. -The glossohyal is a spatulate bone 

 underlying the tongue and overlying the first 

 basibranchial bone at the anterior end of the 

 branchial arch (see Figure 49). Cybiosarda and 

 Orcynopsis have a pair of oval tooth patches on the 

 dorsal surface of the glossohyal (Figure 43a, b). 

 Gymnosarda also has a pair of tooth patches on the 

 tongue, but they are on plates over the glossohyal 

 and are not fused to the bone (Figure 43f). The 

 ventral surface of the tooth patches of Gymnosar- 

 da have a deep longitudinal ridge which fits the 

 ventral ridge of the glossohyal laterally. On the 

 dorsal surface of the glossohyal of Gymnosarda, 

 there is a prominent longitudinal ridge on which 

 the paired tooth patches meet. The size of the tooth 

 patches may vary from one side to the other as in 

 the specimen of Orcynopsis unicolor illustrated 

 (Figure 43b). Sarda lacks tooth patches (Figure 



564 



