FISHERY BULLETIN: VOL. 79. NO. 4 



threshers in Table 3, in the form A + B/C + D, 

 where A and B are the numbers of rows in the 

 upper left and right jaw halves, and C and D the 

 numbers in the lower left and right jaw halves. 

 Also presented are total tooth row counts, in the 

 form Ab/Cd, where Ab is the total number of upper 

 rows and Cd the total lower rows. For dental 

 formulas of 10 bigeye threshers the ranges, 

 means, and standard deviations are 11-12 

 (11.7±0.5) + 10-12 (11.5±0.7)/10-12 (10.8±0.8) 

 + 10-12 (10.7±0.7). For the same number of total 

 counts the ranges, means, and standard deviations 

 are 20-24 (23.2±l.l)/20-24 (21.5±1.4). 



Using Applegate's (1965) and Compagno's 

 (1970) terminology for tooth row groups, the 

 dentition of the bigeye thresher can be divided 

 into two rows of anteriors (A) at either side of the 

 symphysis and 8-10 rows of lateroposteriors (LP) 

 on either side and postlateral to them (in both 

 upper and lower jaws. Figure 7). An expanded 

 formula for the bigeye thresher is: 



LP9-10 + A2 + A2 + LP8-10/LP8-10 



+ A2 + A2 + LP8-10 (Figure 8). 



Anterior teeth of threshers differ from lateral 

 and posterior teeth in having narrower crowns 

 relative to their height and more erect cusps, but 

 they are less well differentiated in Alopias than 

 in lamnids, odontaspidids, mitsukurinids, and 



pseudocarchariids. The lateroposterior teeth of 

 the bigeye thresher vary towards the dental band 

 (gradient monognathic heterodonty), becoming 

 smaller, lower relative to width, more oblique- 

 cusped, more convex along the premedial edge, 

 and more deeply notched in the postlateral edge, 

 with the postlateral blade tending to change into 

 cusplets on the more postlateral rows. Posterior 

 teeth are not well differentiated from laterals in 

 the bigeye thresher and are not separated out in 

 the expanded formula; upper intermediate teeth 

 and upper and lower symphyseal teeth are absent. 



Teeth in the upper jaw are not markedly dif- 

 ferent in shape from lowers, but are slightly 

 larger. All teeth are compressed, sharp-edged, and 

 bladelike, and have narrow-based cusps. 



Bass et al. (1975) suggested that in A. super- 

 ciliosus the teeth of females are somewhat broader 

 than those of males, reflecting gynandric or sexual 

 heterodonty (dental sexual dimorphism; see Com- 

 pagno 1970). Comparison of the jaws of an adult 

 female with those of a large adult male (Figures 

 9, 10) shows that males have teeth (especially the 

 anteriors and more premedial lateroposteriors) 

 with higher, more flexed cusps than females. 

 Gruber and Hubbeir (unpubl. data) have exam- 

 ined a number of jaws from male and female 



^Gordon Hubbell, Director, Candron Park Zoo, Miami, 

 FL 33149. 



Table 3. — Dental formulas of Alopias superciliosus. 



Abbreviations: CAS, California Academy of Sciences, San Francisco, Calif.: CBAT, Centre Biologia Aquatica Tropica, Lisbon; GH-A, Gordon 

 Hubbell, Alopias jaw collection; LACM, Los Angeles County Museum of Natural History, California; LJ\/C, L. J. V Compagno collection; MBP, Museu 

 Socage. Portugal; MCZ, Museum of Comparative Zoology, Harvard University, Massachusetts; SHG-A, Samuel H Gruber, Alopias collection. 

 WNA, western Nortti Atlantic; ENA, eastern Nortti Atlantic; ESA, eastern South Atlantic; SWI, southwestern Indian; WNP western North Pacific; ENR 

 eastern North Pacific; ECP, eastern Central Pacific. 

 ^We doubt that this was a mature adult. 



Cadenat (1956) mentioned that 1 or 2 teeth were missing on each side of this specimen. 



Fitch and Craig (1964) give 9 + 10/10 + 10 for this specimen, but we found that they apparently missed 3 rows of upper teeth. 



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