GRUBER and COMPAGNO: TAXONOMIC STATUS AND BIOLOGY OF BIGEYE THRESHER 



fins, possible misinterpretation of the actual size 

 of these fins in A. profundus. 



The relative positions of the anal and second 

 dorsal fins vary. The account and illustration of a 

 130 cm TL A . superciliosus from Cuba in Bigelow 

 and Schroeder (1948, figure 5) shows the free rear 

 tip of the second dorsal fin terminating anterior to 

 the anal origin by a distance about equal to the 

 second dorsal base. Nakamura's (1935) illus- 

 tration of an adult A. profundus (pi. 1, figure 1) 

 indicates that the dorsal rear tip extends posterior 

 to the anal base, but his illustration of a fetal 

 A. profundus (pi. 2, figure 3) shows that it is about 

 opposite the anal origin. Cadenat (1956, figure 

 3B-C) illustrated two fetuses of A. superciliosus 

 from Senegal, one with the rear tip over the rear 

 end of the anal base and the other with it over the 

 middle of the anal base. Bass et al. (1975, figure 

 19) pictured a South African specimen of 

 A . superciliosus with the tip about over the anal 

 origin. Our 356 cm TL specimen (SHG-A2) from 

 Florida also had the rear tip about opposite the 

 anal origin, but her two fetuses have the rear tip 

 slightly anterior to the anal fin origin. Two 

 specimens from the eastern Central Pacific 

 (SM-9-II-64-3 and LJVC-0355), respectively, had 

 the tip anterior to the anal origin and over the first 

 third of the anal base. 



Accounts of bigeye threshers such as those of 

 Springer (1943), Bigelow and Schroeder (1948), 

 Cadenat (1956), Fitch and Craig ( 1964), Kato et al. 

 (1967), Telles (1970), and Bass et al. (1975), and 

 the specimens examined by us show the pelvic fins 

 to be very large and about the size of the first 

 dorsal fin, but Nakamura's (1935, pi. 1, figure 1) 

 line drawing of an adult female A. profundus 

 shows a minute pelvic fin, less than one-fourth of 

 the area of the first dorsal fin. Curiously, the 

 pelvic fins in Nakamura's (pi. 2, figures 3, 4) 

 drawings of a 71 cm fetus of A . profundus have the 

 proportions of other bigeye threshers and are 

 about as large in area as the first dorsal fin. Yet 

 Nakamura described the pelvic fins of both adults 

 and fetuses in the same words, "ventral fins 

 moderate" (p. 2, 5). In the absence of pelvic 

 fin measurements in Nakamura's account, we 

 suspect that the unusually small pelvic fins pic- 

 tured in his adult A. profundus may be erroneous 

 and are perhaps due to the difficulties of accu- 

 rately drawing a large shark, without special 

 techniques and perhaps under trying circum- 

 stances (i.e., in a fish market). The drawing of the 

 fetal A . profundus seems more accurate and may 



reflect the writer's ability to study and draw it in 

 his laboratory. Possibly the large adult specimen 

 of A. pelagicus sketched by Nakamura (pi. 1, 

 figure 2) was also drawn with undersized pelvics, 

 at least in comparison with the photograph of a 

 specimen by Bass et al. (1975, figure 17), and with 

 photographs and specimens of A . pelagicus seen 

 by Compagno. The fetal specimen of "A. pelagic us" 

 illustrated by Nakamura (1935, pi. 3) is of no help 

 here as it appears to be a specimen of A. vulpinus 

 (unlike the adult). 



The supposed differences in the contour of the 

 anterior margin of the first dorsal fin are probably 

 size-related, the contour becoming straighter with 

 increase in size. The adult A . profundus pictured 

 by Nakamura (1935) has a nearly straight ante- 

 rior margin, while in the fetal specimen it is 

 strongly convex. This applies likewise to the 

 356 cm TL Miami specimen (SHG-A2) of A. 

 superciliosus and to the two fetuses taken from 

 her. This change also occurs in A . vulpinus (com- 

 pare the juvenile pictured in Bigelow and Schroed- 

 er [1948] with the adult in Bass et al. [1975]) and 

 A. pelagicus , as well as some other lamnoid 

 sharks, such as Isurus oxyrinchus (Garrick 1967, 

 figure 6). 



The lower precaudal pit appears to be variably 

 present or absent in bigeye threshers, as sug- 

 gested by Bass et al. (1975). The lower pit was 

 present in possibly all of the three adults of 

 A. profundus, 332-366 cm TL, studied by Naka- 

 mura (1935), though it is not specifically men- 

 tioned in his account of a fetal A. profundus and 

 not shown in his illustration (pi. 2, figure 1). It was 

 also present in a 372 cm TL adult male from 

 California (CAS-1963-X: 7) studied by Fitch 

 and Craig (1964) but absent in all our Miami 

 specimens and absent in two specimens from the 

 eastern Central Pacific (SM-9-II-64-3 and 

 LJVC-0355). We suspect that the lower precaudal 

 pit is present only in some adult or subadult 

 bigeye threshers, as it has not occurred so far in 

 fetal or very small, free-living specimens. The 

 upper precaudal pit is less well-marked in small 

 specimens than in large subadults and adults. 



DESCRIPTIVE NOTES 



Proportional measurements of 13 bigeye thresh- 

 ers, including 6 reported by us, are given as 

 proportion of precaudal length in Table 1, rather 

 than total length, as the tail length is apparently 

 quite variable relative to body length. Writers 



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