COLLETTE ET AL.: BELONIFORMES 



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BODY LENGTH (mm) 



Fig. 178. Relative growth of upper jaw in Belone belone. Lower jaw extension as a percent of head length plotted against body length. Inset 

 is of a 43.7 mm BL B. belone from Ireland in the "halfbeak" stage. (From: Collette and Parin. 1970.) 



The lower jaw is even shorter in Melapedalion and virtually 

 absent in adult Chriodorus and Oxyporhamphus. Chriodorus 

 looks superficially more like an atherinid than a halfbeak, hence 

 its specific name of at herinoides. Adult Oxyporhamphus resem- 

 ble flyingfishes because of the enlarged pectoral fins. Juveniles 

 of all four genera have a distinct beak. Arrhamphus, Melape- 

 dalion. and Chriodorus have always been considered halfbeaks. 

 Oxyporhamphus has usually been considered an exocoetid or 

 placed in a separate family.' Even with its short beak, Arrham- 

 phus varies geographically in beak length: Arrhamphus s. scler- 

 olepis of northern Australia has a proportionately shorter lower 

 jaw (up to 20 times in head length) than does A. sclerolepis 

 krefflii of southern Queensland and New South Wales (up to 1 1 

 times in head length, see Collette, 1974b: fig. 4). 



Exocoetidae.— The two most primitive genera of flyingfishes, 

 Fodiator and Parexocoetus, have an elongate lower jaw (Parin, 



' Parin (1961), although still recognizing the Oxyporhamphidae as 

 valid, clearly showed that Oxyporhamphus is a halfbeak, even though 

 it has a straight margin to the upper jaw instead of triangular as in other 

 halfbeaks. Two developmental characters support placement of O.vr- 

 porhamphus in the Hemiramphidae: a preanal fin fold is present in 

 larvae (absent or lost soon after hatching in Exocoetidae) and the pelvic 

 fins form last (pectoral fins form last in Exocoetidae). 



1961; Kovalevskaya, 1982). This clearly is a beak m juvenile 

 (15-55 mm SL) Fodiator, which like several genera of halfbeaks, 

 lose their beaks as they grow larger (Fig. 1 8 1 C and Breder, 1938: 

 figs. 5 and 6E). A beak is present in Parexocoetus mento (Imai, 

 1959). Small ( 1 9-20 mm) P. hrachypterus have a pair of barbels 

 that are attached to the ventral surface of the beak and obscure 

 it (Fig. 182). Thus, a beak which is absent in advanced flying- 

 fishes, is present in both primitive genera. 



Juvenile stages of many exocoetids develop barbels on the 

 lower jaw (Table 91). Barbels range from relatively short to 

 longer than body length (Fig. 181D-I). Parexocoetus mento 

 does not develop a barbel nor do species of Prognichthys and 

 Hirundichthys (Kovalevskaya, 1982). Paired barbels develop in 

 Parexocoetus hrachypterus and in all species of Cheilopogon 

 (Fig. 181D, G-I; Kovalevskaya, 1982). In species of Cheilo- 

 pogon (subgenus Procypselurus, Ch. nigricans group), the bar- 

 bels consist of a thick strand with a leathery fold branching oflT 

 it in the form of a lobe (Parin, 1961; Kovalevskaya, 1982). In 

 small specimens of Ch. cyanopterus the barbel may be complex 

 and have 2-3 flaps. Members of Cheilopogon (subgenus Mac- 

 ulocoetus) have flattened barbels, joined together at the base. 

 These may be large. The barbels of C/!«7opo^o« (subgenus Pten- 

 ichthys) range from short (in Ch. heterurus doederleini) to long 

 (in Ch. unicolor). The barbels in Cheilopogon pinnatibarbatus 



