FISHERY BULLETIN: VOL. 73. NO. 3 



Allothunnus has keels on the fourth to seventh; 

 Gymnosarda, Sarda australis, S. orientalis, and S. 

 chiliensis all have them on the four vertebrae 

 between the fourth and eighth. Correlated with its 

 greatly increased number of vertebrae (Table 9), 

 Sarda sarda has keels on the 5th to 10th preural 

 vertebrae. 



Caudal Complex 



Posterior to the peduncular vertebrae, the sup- 

 porting bones of the caudal fin (Figure 56) consist 

 of four preural centra. Preural centra four and 

 three bear stout haemal and neural spines. Preural 

 centrum two has a haemal spine and a fused 

 epural. The urostyle represents a fusion of preural 

 centrum one and the ural centrum (Potthof f 1975). 

 The urostyle is fused with a triangular plate 

 posteriorly and with the uroneural anteriorly. 

 Dorsally, the urostyle bears an autogenous epural 

 and ventrally, the autogenous parhypural. Preural 

 centra two to four are compressed in all bonitos, as 

 in Thunnus. Usually, two neural and three haemal 

 spines bend abruptly away from the vertebral axis 

 on these preural centra and parallel the dorsal and 

 ventral edges of the hypural plate. Exceptions are 

 found in some specimens of S. sarda and S. 

 chiliensis (Figure 56c), which have an additional 

 pair of neural and haemal spines from preural 

 centrum five supporting caudal rays. The figure of 

 S. sarda presented by Monod (1968, fig. 749) has 

 two haemal spines on preural centrum three which 

 is an anomaly. Other elements of the preural cen- 

 tra are described in the sections on the vertebral 

 column and caudal peduncle keels. 



The triangular hypural plate is composed of five 

 fused hypural bones (Potthoff 1975). The dorsal- 

 most (hypural 5) is not completely fused with the 

 hypural plate in the bonitos (Figure 56c) or in the 

 higher tunas, Auxis to Thunnus. The primitive 

 hypural notch is absent from the middle of the 

 posterior margin in all bonitos except for a vestige 

 in Gymnosarda. The anterior epural (epural one) 

 resembles the neural spine of the adjacent preural 

 centrum three because it is secondarily fused to 

 the neural arch of the second preural centrum. The 

 posterior epural (epural two) is a free splint locat- 

 ed between the anterodorsal margin of the 

 hypural plate and the anterior epural in the Sar- 

 dini (Figure 56b). It is absent (or may be second- 

 arily fused to the anterior epural) in one Tunisian 

 specimen of S. sarda (Figure 56d), which is an 

 anomaly. 



The parhypural has a strong hooked process, the 

 parhypurapophysis, at its proximal end. As in 

 Thunnus, it is located between the first haemal 

 spine and the anteroventral margin of the hypural 

 plate in all bonitos, except Gymnosarda. In Gym- 

 nosarda (Figure 56e), the parhypural is fused with 

 the hypural plate as in Acanthocybium and some 

 species of Scomber omorus. Kishinouye's (1923) 

 figures of Gymnosarda (fig. 38) and 

 Acanthocybium (fig. 39) are similar to our obser- 

 vations, but the caudal complex is upside down in 

 his figure of Gymnosarda. Fusion of the 

 parhypural with the hypural plate in 

 Acanthocybium was also noted by Conrad (1938) 

 and Fierstine and Walters (1968). In 

 Scomberomorus niphonius, we also find this 

 fusion, which is in agreement with Kishinouye's 

 (1923) fig. 41. However, the parhypural is not fused 

 with the hypural plate in Scomberomorus chinense 

 (Kishinouye 1923, fig. 40) and the three western 

 Atlantic species of Scomberomorus described by 

 Mago Leccia (1958). The shape of the 

 parhypurapophysis separates Cybiosarda, Or- 

 cynopsis, and Gymnosarda from Sarda and 

 Allothunnus. The former have a smooth oblique 

 anterior margin and the latter are concave. The 

 concentrations of tendons and muscular bands 

 between the parhypurapophysis and caudal rays in 

 scombroids were described by Fierstine and 

 Walters (1968), but no specific study of this aspect 

 was made during our work. 



One of the diagnostic characters of the 

 Scombridae is that the bases of the caudal rays 

 cover the hypural plate (Figure 57), instead of only 

 extending part way over the plate as is true of the 

 Gempylidae and Trichiuridae. Another diagnostic 

 character of the Scombridae is that four preural 

 centra support the caudal rays (Figure 57). In the 

 Gempylidae, Carangidae, and Coryphaenidae, 

 only three preural centra support the caudal fin 

 rays (Berry 1969; Potthoff 1975). 



DORSAL AND ANAL FINS 



Scombrids have two dorsal fins. The first dorsal 

 fin is composed of stiff spines and is separated 

 from the second dorsal by a short distance, except 

 in Rastrelliger, Scomber, and Auxis which have a 

 greater distance between the fins. The second 

 dorsal fin is composed of soft rays and is followed 

 by a series of free finlets, 6-10 in the Sardini. The 

 anal fin is located approximately opposite the dor- 

 sal fin and is composed largely of soft rays 



578 



