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



side of one hyomandibula of a Tokyo specimen of 

 S. orientalis, the spine was short as in S. chiliensis. 

 We found one specimen of S. chiliensis from 

 Callao, Peru in which the spine projected as in S. 

 orientalis. Thus, this difference is not absolute but 

 "corroboratory" as Godsil has noted. Cybiosarda 

 (Figure 39a) and Gymnosarda (Figure 39e) 

 resemble S. chiliensis but the spine is still shorter. 

 The ridge forms an angle but no spine is present in 

 Orcynopsis (Figure 39b) and Allothunnus (Figure 

 39f). 



The lateral condyle is broader in Allothunnus 

 than in other bonitos, and its lower anterior ver- 

 tical margin, where the metapterygoid attaches, 

 does not project as far (Figure 39f). Also, the 

 groove into which the preopercle fits is more 

 curved in Allothunnus. 



Symplectic.-The symplectic is a small bone that 

 fits into a groove in the quadrate (Figure 9). Boni- 

 tos fall into three groups based on the shape of the 

 symplectic. Orcynopsis, Cybiosarda, and Sarda 

 (Figure 40a-d) have a wider upper part with a 

 pointed or "flared" anterodorsal projection as in 

 Thunnus. Gymnosarda has a rather thick upper 

 part and only a slight lateral expansion about the 

 middle of the anterior margin (Figure 40e). The 

 anterolateral expansion of the symplectic is better 

 developed in Allothunnus (Figure 40f) than in 

 Gymnosarda, but there is no anterior projection at 

 the upper end. 



In external view, there is a longitudinal axis to 

 the symplectic which is shaped differently in the 

 three groups. Gymnosarda has a much thicker 

 upper end. The upper part is also thick but 

 somewhat flattened in Allothunnus as also noted 

 by Nakamura and Mori (1966). Orcynopsis, 

 Cybiosarda, and Sarda all have a notch at about 

 the middle of the axis on the external surface of 

 the bone which is absent in Gymnosarda and 

 Allothunnus. 



Figure 40.-Right symplectics of six species of Sardini, left 

 figure of each pair is the external view, right the internal 

 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 chiliensis, Callao, Peru, 

 437 mm FL. e. Gymnosarda unicolor, Truk Islands, 775 mm 

 FL. f. Allothunnus fallai, Tasmania, 775 mm FL. a-e drawn 

 twice as large as f . 



base is expanded more than in other genera of 

 bonitos. 



Quadrate. -The lower jaw is suspended from the 

 cranium by means of the articulating facet of the 

 ventral surface of the triangular quadrate (Figure 

 9). The quadrates are similar in all bonitos, with a 

 deep groove where the symplectic fits along the 

 inner posterior margin and a posterodorsal process 

 (Figure 41). The quadrate of Allothunnus has a 

 distinctly longer posterodorsal process resembling 

 those in Thunnus. The process in Gymnosarda 

 (Figure 41e) has a slightly broader tip and also its 



Hyoid Complex.— This complex, as discussed 

 here, includes the hypohyal, ceratohyal, epihyal, 

 and interhyal bones and the seven branchiostegal 

 rays (Figure 42). The external view of the four 

 bones in Sarda orientalis and Gymnosarda 

 unicolor has been previously illustrated by 

 Kishinouye (1923:326) along with the hyoid arches 

 of six other genera of Scombridae. 



The hypohyal is composed of a dorsal and a 

 ventral segment fused longitudinally along a 



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