FISHERY BULLETIN: VOL. 73, NO. 3 



RADIALS 



SCAPULA 



CORACOID 



CLEITHRUM 



Figure 62.-Left pectoral girdles of two species of Sardini, in- 

 ternal view. a. Sarda sarda, Azores, 418 mm FL. b. Cybiosarda 

 ekgans, New South Wales, 360 mm FL. 



Gymnosarda the inner shelf stops abruptly at the 

 middle portion where the marginal ridge begins. 



Scapula 



The anterior margin of the scapula fits into the 

 inner shelf of the cleithrum (Figure 62). This at- 

 tachment extends to the posterior projecting plate 

 anterodorsally. The scapula is attached with the 

 coracoid posteriorly and dorsally it is attached 

 with the first two and part of the third upper 

 radials (Figure 63). The posterior margin of the 

 scapula is drawn out into a facet which accepts the 

 anterior ray of the pectoral fin. A suture bisects 

 the scapula through the scapular fenestra. The 

 general features of the scapula are similar among 

 the bonitos. The scapular fenestra of Gymnosarda 

 (Figure 63e) is relatively larger, and that of the 

 species of Sarda (Figure 63c, d) is smaller, than the 

 other bonitos. 



Coracoid 



The coracoid is elongated and more or less 

 triangular in shape (Figure 63). It is connected 

 with the scapula along its flat dorsal edge in 

 AUothunnus (Figure 63f ). In all other bonitos, this 

 margin is interrupted ventral to the scapular 

 fenestra and extends dorsally as an interdigitat- 

 ing suture. The ventral wing of the coracoid is 

 xiphoid with a V-shaped depression along the 

 midline. The coracoid has two points of attach- 

 ment with the cleithrum, the first along the 

 anterior margin near the scapula, and the second 

 at the anterior end of the ventral wing. The mar- 



gin of the coracoid, between its articulations with 

 the cleithrum, is curved inward. This curvature is 

 more pronounced in Gymnosarda (Figure 63e) 

 than in the other bonitos, which resemble Thun- 



nus. 



Radials 



The four radials differ in size and shape and are 

 attached directly to the thickened posterior edges 

 of the scapula and coracoid (Figures 62, 63). The 

 size of the radials increases ventrally. Two small 

 foramina are located between the second and 

 third, and the third and fourth radials, counting 

 downward. The first two radials and the upper half 

 of the third radial attach to the coracoid; the ven- 

 tral half of the third plus the fourth radial attach 

 to the scapula. A fenestra is present between the 

 dorsoposterior end of the coracoid and the largest 

 radial, which has a prominent posteroventral 

 process in all bonitos except Sarda and AUothun- 

 nus. In both characters, the fenestra and the last 

 radial process, Sarda and AUothunnus resemble 

 Thunnus; the other bonitos resemble 

 Acanthocybium. 



Pectoral Fin Rays 



The first (and largest) pectoral ray articulates 

 directly with a posterior process of the scapula. 

 The other rays attach to the radials. Within the 

 Scombridae, the number of pectoral fin rays 

 increases from the more primitive members of the 

 family to the more advanced: Scombrini 18-21, 

 Scomberomorini 20-25, Sardini 21-28, Thunnini 

 (except for Thunnus) 22-29, Thunnus 30-36. 

 Within the Sardini (Table 13), Orcynopsis and 

 Cybiosarda have the fewest pectoral fin rays 

 (modes of 22 and 23, respectively). Gymnosarda 

 has the most (25-28), followed by one species of 

 Sarda {S. australis, 25-27), and AUothunnus 

 (24-26). The other three species of Sarda are in- 

 termediate with species modes of 24 or 25. 



Postcleithrum 1 and 2 



The posterior projecting plate of the cleithrum 

 has its posterior end attached to the curved first 

 postcleithrum, which connects to another bone, the 

 second postcleithrum. Both postcleithra are thin 

 and bent. Postcleithrum 1 (the upper one) has a 

 narrow anterodorsal end and a broad posteroven- 

 tral body (Figure 64). Gymnosarda has a pointed 



586 



