FISHERY BULLETIN: VOL. 79. NO. 4 



FIGURE 9.— Upper right anterior teeth 1 through 5 of a 381 cm TL female Alopias 

 superciliosus iGH-A2) showing that the typical female shape is broader, less .sinuous and 

 somewhat flatter than its male counterpart. The cu.sp height of the 3d anterior tooth was 

 1.20 cm. Photo: F. Karrenburg. 



FIGURE 10. — Upper right anterior teeth 1-5 of a 342 cm TL male Alopias xupemlio.'itif: 

 (GH-A4). These elongate, narrrow flexed cusps are typical of males and when compared 

 with the female above one can clearly see the gynandric heterodonty in this species. The 

 cusp height of the third anterior tooth was 1.45 cm. Photo: F. Karrenburg. 



having an oval or nearly circular crov^^n with a 

 strong medial ridge and posterior cusp, a pair of 

 weaker lateral ridges, and variably developed 

 lateral cusps (Figure 11). The crowns of these 

 denticles are connected to their bases (buried in 

 the skin) by tall, broad pedicles. The specimen of 

 A. pelagicus examined has smaller denticles 

 with less prominent lateral cusps than the two 

 specimens of A. superciliosus and three A. vul- 

 pinus examined. 



SIZE 



The bigeye thresher grows to a large size as an 

 adult; the heaviest reliably reported was a 284.5 

 kg female from Cuba (Guitart Manday 1975). 

 Grey (1928) stated that one from New Zealand 

 weighed 640 lb (290 kg). Using the length-weight 



equation for bigeye threshers given in Guitart 

 Manday (1975) 



5 T 3.448534 



W =0.1825 X 10-^L 



L = 3.448534 (W/1.825 x 10 



or 



6 



(1) 



where W is weight in kilograms and L is pre- 

 caudal length in centimeters; the weight of Gui- 

 tart Manday's largest bigeye thresher corresponds 

 to a precaudal length of 237 cm and a total length 

 of about 452 cm, while that of Grey's 290 kg bigeye 

 thresher corresponds to a precaudal length of 240 

 cm and a total length of about 458 cm. Total 

 lengths for these specimens were estimated by 

 averaging the ratio of dorsal caudal and precaudal 

 lengths for 10 specimens of large subadult and 

 adult threshers in Table 1, 270-460 cm TL, which 



gives Lcaudal = 0.908±0.079 SD.Lprecaudal- 



628 



