342 



ONTOGENY AND SYSTEMATICS OF FISHES- AHLSTROM SYMPOSIUM 



Fig. 177. Beloniform larvae. (A) Adrianichthyidae: Oryzias melastigma. 4.3 mm; (B) Scomberesocidae: Cololabis saira. SWFC 5009-50. 1 10, 

 5.1 mm SL; (C-D) Belonidae; (C) Strongylura exilis. LACM 42756-5, 8.6 mm SL; (D) Xenemodon cancila. 9.6 mm SL ANSP 124230: (E-F) 

 Hemiramphidae: (E-F) Hyporhamphus rosae. 5.7 mm SL, LACM 42870-5; (G-H) Exocoetidae: (G) Cheilopogon pinnatibarbatus califonucus. 

 LACM IP77-3, 3.7 mm SL; (H) Cheilopogon katoptron. 3.2 mm SL. From: (A) Job, 1940; (B-G) Original: (H) Kovalevskaya, 1965. 



Nanichthys. A slight beak develops in Cololabis; Elassichthys 

 does not develop a distinct beak. 



Belonidae. — Most species of Belonidae pass through a "half- 

 beak" stage in which the lower jaw, but not the upper jaw, is 

 greatly elongate. Juveniles of Belone belone remain in the half- 

 beak stage for a longer time than other needlefishes. This has 

 led directly to four synonyms of Belone belone described as 

 halfbeaks (CoUette and Farin, 1 970: 1 6-17). Plotting the relative 

 length of the lower jaw extension, as a percentage of head length 

 against body length (Fig. 1 78), shows that lower jaw extension 

 in B. belone may be nearly 150% of head length at 25 mm BL 

 (body length) and decreases to less than 10% by 175 mm BL. 

 Petalichthys and Platybelone (Fig. 179E) also remain in the 

 halfbeak stage for a long time. The duration of the halfbeak 

 stage varies among species of Strongylura (Fig. 1 79C and F). 



Comparative development of Platybelone {as Strongylura long- 

 leyi), Strongylura marina, S. nolata, and two species of Tyto- 

 surus, (T. acus and T. crocodilus. Fig. 179G and J) was illus- 

 trated by Breder ( 1 932: figs. 7 and 1 0, plates 1 and 2). Tylosurus 

 crocodilus (Fig. 1 79J) completely lacks a halfbeak stage, upper 

 and lower jaws growing at the same rate from larval to adult 

 stages of development (Breder, 1932: plate 2, fig. 2, as T. ra- 

 phidoma). The South American freshwater genus Belonion 

 (maximum size 42 mm body length) is characterized by ma- 

 turing while still in the halfbeak stage (Fig. 1 79A-B) and was 

 considered paedomorphic by Collette (1966). 



Hemiramphidae.— Adults of four genera of halfbeaks lack the 

 elongate lower jaw that characterizes most members of the fam- 

 ily. The lower jaw extends only 1.5-1 1.0 mm beyond the upper 

 jaw throughout the size range in Arrhamphus (Collette, 1974b). 



