HUBBS and WISNER REVISION OF THE SAURIES 



2b. Jaws only moderately produced into blunt beaks, the lower slightly longer. Maximum 



size about 400 mm SL. Native only in North Pacific Ocean Cololabis saira 



3a. Jaws of adults produced as slender beaks, the lower about twice the length of upper. 

 Gill rakers 22-24 (19-26). Procurrent caudal rays 4 (3-5i. Maximum size to 126 mm, 

 usually about 100 mm. Known only from warm-temperate waters of Atlantic and 

 Indian Oceans Nanichthys simulans 



3b. Upper jaw very little produced, bluntly rounded, the lower jaw slightly more produced 

 and more pointed at all sizes. Gill rakers 17-18 (15-21). Procurrent caudal rays 2-3. 

 Maximum size to 68 mm SL. Known only from eastern tropical Pacific and westward to 

 Hawaii Elassichthvs adocefiis 



AIDS TO IDENTIFICATION 



If the specimen is determined to be one of the 

 larger species, pertinence to S. saurus or C. saira 

 will be obvious from the oceanic source of the 

 material, and, for all but the very young, from the 

 presence or absence of a beak (Figure 2); even if 

 the long beaks of Scomberesox are broken off near 

 the base the stubbed condition will be obvious. 

 However, if the very young of one or both species 

 should be taken in the eastern Pacific Ocean in the 

 upwelling area along the Equator (which now 

 seems unlikely from the distributional evidence 

 discussed below), it would hardly be feasible to 

 arrive at a certain identification on the basis of 

 beak development alone until the beak begins to 

 develop at about 40 mm SL; but the reduced num- 

 bers of pectoral and procurrent caudal rays and of 

 gill rakers (rather short and widely spaced) read- 

 ily distinguish Elassichthvs from Scomberesox 

 and Cololabis. The development of the beak is the 

 most trenchant distinction between Scomberesox 

 and Cololabis; counts (Tables 2-5) and mor- 

 phometric values (Table 6) overlap widely. 



If the specimen is determined to be a dwarf, its 

 pertinence to E. adocetiis or N. simularts will 

 probably always be determineable from the local- 

 ity of capture, and, for specimens longer than 

 about 50 mm, from the incipient to full devel- 

 opment of the beak (Figure 2); in fact, in 

 Elassichthys the upper jaw never becomes really 

 beaklike, only broadly rounded, not moderately 

 pointed as in C. saira of comparable size (Figure 

 4). If further check is desired, separations may be 

 attained by counting gill rakers, pectoral rays, or 

 vertebrae (Tables 2-5). Ueyanagi and Doi (1971) 

 showed that in young of Elassichthys (^=30 mm) 

 the depth of the caudal peduncle was one-half or 

 less of its length, but was about equal in S. saurus 

 and C. saira. We find (original data) N. simulans 

 to have a ratio of depth to length of caudal pedun- 

 cle similar to that of £. adocetus. These ratios hold 

 for all sizes of the four species. 



The scomberesocid fishes inhabiting the Atlan- 

 tic or Indian Oceans may be either N . simulans or 

 S. saurus. determinable by the meristic counts 

 (Tables 2-4). At lengths greater than about 60 mm, 

 the relative development of unbroken beaks 

 should ordinarily be decisive (Figure 2). 



529 



