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



Figure 42.-Hyoid complex (hypohyal, ceratohyal, epihyal, and interhyal) and branchiostegal rays of six species of Sardini, external 

 view of left side. Unlabelled line points to ceratohyal window, a. Cyhiosarda elegans, Western Australia, 422 mm FL. b. Orcynopsis 

 unicolor, Tunisia, 543 mm FL. c. Sarda australis, New South Wales, 495 mm FL. d. Sarda orientalis, Panama, 415 mm FL. e. 

 Gymnosarda unicolor, Truk Islands, 787 mm FL. f . Allothunnus fallai, Tasmania, 778 mm FL. 



43c-e) and the shape and proportions of the glos- 

 sohyal is extremely variable both inter- and in- 

 traspecifically as Godsil (1955) has pointed out for 

 S. chiliensis and S. orientalis. A slightly concave 

 anterior margin is present on the glossohyal of 

 Allothunnus. A depression on the ventral surface 

 of the proximal portion of the glossohyal is present 

 in most bonitos except for Sarda orientalis (Godsil 

 1954, 1955) and Gymnosarda. 



Urohyal.-The urohyal is a median unpaired 

 bone. The anterior end of this element lies 

 between, and is connected with, the hypohyals of 



the left and right sides. The urohyals of the bonitos 

 have a thickened anteroventral margin which 

 gradually narrows posteriorly (Figure 44). Gym- 

 nosarda has a distinctive thickened posterodorsal 

 margin, which starts at the anterior third of the 

 bone and forms a flattened platform at the 

 posterior end. A similar tendency was found oc- 

 casionally in other bonitos, especially Orcynopsis, 

 but the thickening was limited to the middle por- 

 tion of the dorsal margin. Cyhiosarda, Orcynopsis, 

 and Gymnosarda have relatively deep urohyals; 

 Sarda and Allothunnus have relatively elongate 

 urohyals. 



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