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



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Specific Characters.— A fleshy ring (Iwai and 

 Nakamura 1964b) was found along the posterior 

 margin of the olfactory rosettes in some bonitos. 

 This fleshy ring is the continuation of the well- 

 developed distal end of the olfactory laminae and 

 forms a fleshy elevated area in species of Sarda. In 

 S. sarda the fleshy ring usually develops in larger 

 specimens (over 360 mm FL) as a folded fleshy pad 

 (Figure 8h). Different developmental stages of the 

 fleshy pad were found in all species of Sarda ex- 

 cept in S. c. chiliensis which had no apparent rings. 

 No fleshy ring or pad was found in Cybiosarda or 

 Orcynopsis (Figure 8a, b). In Gymnosarda, a very 

 definite fleshy ring surrounds all the olfactory 

 laminae (Figure 8i) except in a juvenile 

 specimen (71 mm FL), which had an elongated oval 

 rosette with only 27 laminae. Nakamura and Mori 

 (1966) found the olfactory rosette of Allothunnus 

 to have labial fleshy rings around the olfactory 

 laminae, similar to our observations (Figure 8j). 



Osteology 



Osteological characters proved to be very useful 

 in determining how many genera of Sardini 

 should be recognized. The osteological description 

 is divided into five sections: skull, axial skeleton, 

 dorsal and anal fins, pectoral girdle, and pelvic 

 girdle. Osteological terminology generally follows 

 de Sylva (1955) and Gibbs and Collette (1967) with 

 a few changes to bring this nomenclature into 

 closer agreement with more modern terminology. 



SKULL 



Description of the skull is presented in two sec- 

 tions: neurocranium and branchiocranium. Figure 

 9 shows an articulated skull of Gymnosarda 

 unicolor in lateral view to provide orientation for 

 the descriptions of the individual bones. 



Neurocranium 



Following a general description of the 

 neurocranium, the four major regions are dis- 

 cussed: ethmoid, orbital, otic, and basicranial. 

 Descriptions of the otoliths are included at the end 

 of this section. 



General Characteristics.— In dorsal view, the 

 neurocranium of bonitos is roughly triangular in 

 shape. The interorbital and otic regions are not as 



533 



