COLLETTE and CHAO: SYSTEMATICS AND MORPHOLOGY OF THE BONITOS (SARDINI) 



projection of the ectopterygoid is longer than the 

 dorsal projection except in Allothunnus which has 

 a larger dorsal projection. The ridge extending 

 from the main axis to the tip of the ventral 

 projection has a sharper angle in Allothunnus 

 compared to the smooth curve in the other bonitos. 

 The main shaft of the ectopterygoid is thicker and 

 higher in Gymnosarda than in the other bonitos. 

 Sarda orientalis has the dorsal projection slightly 

 expanded instead of pointed as in the other species 

 of Sarda. 



Entopterygoid.-The entopterygoid is elongate 

 oval in shape in all the bonitos (Figure 37). The 

 external margin of the entopterygoid is the 

 strongest and thickest part of the bone, and there 

 is a bent posterior end which attaches to the ec- 

 topterygoid externally. Allothunnus has a more 

 elongate entopterygoid and Gymnosarda has a 

 broader one than the other bonitos. 



the inner surface of the bone into which the 

 anterodorsal process of the symplectic fits. The 

 metapterygoid of Gymnosarda is more elongate 

 and triangular in shape and has no projection 

 along the posterior margin. In Allothunnus, the 

 anteroventral and posteroventral margins are 

 very similar to those in Thunnus (Gibbs and 

 Collette 1967, fig. 7). 



HYOID ARCH.-The hyoid arch is the chain of 

 bones that connect the lower jaw and the opercular 

 apparatus with the skull. The arch is composed of 

 the hyomandibula, symplectic, quadrate, hyoid 

 complex (basihyal, ceratohyal, epihyal, interhyal, 



a 



Figure 37.-Left entopterygoids of six species of Sardini, dorsal 

 view. a. Cybiosarda elegans, New South Wales, 355 mm FL. b. 

 Orcynopsis unicolor, Tunisia, 573 mm FL. c. Sarda australis, 

 New South Wales, 363 mm FL. d. Sarda sarda, Azores, 504 mm 

 FL. e. Gymnosarda unicolor, Truk Islands, 772 mm FL. f. 

 Allothunnus fallal, Tasmania, 778 mm FL. a-d drawn twice as 

 large as e and f . 



Metapterygoid. -The posterior and dorsal mar- 

 gins of the metapterygoid articulate with the 

 hyomandibula (Figure 9). A groove is present on 

 almost the entire posterior margin in all bonitos 

 except Allothunnus, which has a deeper and wider 

 groove on the upper half of the posterior margin, 

 as in Thunnus. Cybiosarda, Orcynopsis, and Sarda 

 have a thin projection along the upper half of the 

 posterior margin extending from the internal 

 surface of the metapterygoid (Figure 38). These 

 three genera also have a posteroventral notch on 



Figure 38.-Left metapterygoids of six species of Sardini, in- 

 ternal view. a. Cybiosarda elegans. New South Wales, 355 mm 

 FL. b. Orcynopsis unicolor, Tunisia, 645 mm FL. c. Sarda 

 orientalis, Tokyo, 500 mm FL. d. Sarda sarda, Tunisia, 504 mm 

 FL. e. Gymnosarda unicolor, Truk Islands, 696 mm FL. f. 

 Allothunnus fallai, Tasmania, 778 mm FL. 



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