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



Figure 47.— Left preopercles of six species of Sardini, external 

 view. a. Cybiosarda elegans, Western Australia, 422 mm FL. b. 

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

 New South Wales, 495 mm FL. d. Sarda ckiliensis, Callao, Peru, 

 517 mm FL. e. Gymnosarda unicolor, Amirante Islands, 713 mm 

 FL. f . Allothunnusfallai, California, 680 mm FL. 



with the posterior ends of their respective 

 hypobranchials. The fourth is more irregular and 

 attaches to a cartilage posterior to the third 

 basibranchial. The fifth ceratobranchial is also at- 

 tached to the cartilage, has a dermal tooth plate 

 fused to its dorsal surface, and the complex is 

 termed the lower pharyngeal bone. It is covered 



Figure 48.— Left interopercles of six species of Sardini, external 

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

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

 New South Wales, 475 mm FL. d. Sarda sarda, Tunisia, 504 mm 

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

 Allothunnus fallai, California, 680 mm FL. 



with small conical teeth that are directed slightly 

 posteriorly. Allothunnus has the smallest pharyn- 

 geal teeth among the bonitos. 



Epibranchials.-The four epibranchials are at- 

 tached basally to the ceratobranchial of their res- 

 pective gill arch. They vary in shape with the first 

 one being long and slender like a short cera- 

 tobranchial, the second and third shorter and 

 stubbier, and the fourth one almost V-shaped. 



Pharyngobranchials. -There are four pharyn- 

 gobranchials attached basally to the epibranchial 

 of their respective gill arch. The recurved first one 

 articulates dorsally with the parasphenoid and is 

 frequently referred to as the suspensory pharyn- 

 geal (Iwai and Nakamura 1964a). The triangular 

 second pharyngobranchial bears a patch of small 

 teeth. The third and fourth pharyngobranchials 

 both have dermal tooth plates fused to them and 

 are termed upper pharyngeal bones. 



Gill Rakers. -The hypobranchial, cera- 

 tobranchial, and epibranchials of the first gill arch 

 support a series of slender rigid gill rakers. The 

 longest gill raker is at or near the junction of the 

 upper and lower arches, between the cera- 

 tobranchial and epibranchial. Gill rakers prevent 

 food loss through the opercular gap. There is a 

 correlation between numbers of gill rakers, gap 

 between gill rakers, and size of food items as 



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