FISHERY BULLETIN: VOL. 73, NO. 3 



EPIOTIC 



SPHENOTIC 

 PARIETAL 



SUPRAOCCIPITAL CREST 



ETHMOID 



VOMER 



LATERAL ETHMOID 



FIRST VERTEBRA 

 BASIOCCIPITAL 

 PROOTIC 



BASISPHENOID 



PARASPHENOID 

 Figure 20.-Lateral view of skull of Cybiosarda ekgans, Western Australia, 422 mm FL 



parietal, epiotic, supraoccipital, pterotic, prootic, 

 sphenotic, and intercalar (opisthotic) bones. 



Parietal.— The parietal articulates with the 

 frontal anteriorly, the supraoccipital and the 

 pterotic laterally, sphenotic ventrally, and epiotic 

 posteriorly. The inner lateral crest that originates 

 at the middle of the frontal bones continues 

 through the parietals to terminate at the epiotics. 

 This crest is typical of scombrids but is less 

 developed in Grammatorcynus and in Scomber 

 (Allis 1903). 



Epiotic— The epiotic is massive, irregular, and 

 bounded by the parietal anteriorly, the supraoc- 

 cipital mediolaterally, the exoccipital posteriorly, 

 and the pterotic distolaterally. The inner lateral 

 crest terminates at the posterior end of the epiotic. 

 The medial process of the posttemporal bone is 

 also attached here. The epiotic bones of all the 

 bonitos are similar. 



Supraoccipital. -The supraoccipital can be 

 divided into two parts: a thin, elongate triangular 

 crest and a roughly hexagonal shaped base. The 



supraoccipital crest arises just behind the pineal 

 foramen and extends posterodorsally. In bonitos, 

 the crest extends posteriorly over the first neural 

 spine but usually not over the posterior margin of 

 the first centrum. In Allothunnus the crest ex- 

 tends posteriorly over the second centrum. In dor- 

 sal view, the hexagonal base articulates with the 

 frontal bones anterolaterally, the parietals 

 laterally, and the epiotic posteriorly. Cybiosarda 

 and Orcynopsis have the narrowest and most 

 elongate supraoccipital base; Allothunnus has the 

 shortest and widest. 



Pterotic.-Dorsally, the pterotic is the most 

 posterolaterally located bone. The pterotic ar- 

 ticulates with the epiotic and parietal medially and 

 with the exoccipital and intercalar posteriorly. A 

 sharp posteriorly pointed process is characteristic 

 of the pterotic bone of the bonitos as well as other 

 scombrids. In ventral view, the pterotic articulates 

 with the sphenotic anteriorly and the prootic and 

 intercalar medially. Two fossae, one at the 

 posterior half of the pterotic bone and one at its 

 joint with the sphenotic, seat the dorsal and 

 anterior condyles of the hyomandibula. A deep 



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