350 



ONTOGENY AND SYSTEMATICS OF FISHES-AHLSTROM SYMPOSIUM 



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Fig. 182. Exocoetidae, Parexocoetusbrachypterusbrachypterus. (A) 

 18.1 mm; (B) 19.7 mm. 



lower jaw elongate in juveniles and adults, G2 elongate only in 

 juveniles, and G3 never elongate, even in juveniles. Presence 

 of an elongate lower jaw is considered a synapomorphy of the 

 suborder Exocoetoidei because it is present in the most gener- 

 alized members of each of the four families. This is supported 

 ontogenetically by its presence in juveniles and loss in adults of 

 four genera of Hemiramphidae and in the two least derived 

 subfamilies of Exocoetidae. 



Transformation series H involves elongation of the upper jaw. 

 It is most parsimonious to hypothesize the elongation of the 

 upper jaw as a synapomorphy (H2) of the superfamily Scom- 

 beresocoidea. Thus, the absence of an elongate upper jaw is 

 plesiomorphous (HI) in the Exocoetoidea. 



Transformation series I is the development of barbels in ju- 

 veniles of advanced flyingfishes. State 1 1 is the absence of bar- 

 bels. If we consider barbels in flyingfishes to be derived from 

 the pair of cutaneous lappets on the lower jaw of needlefishes, 

 halfbeaks, and primitive flyingfishes, the most generalized state 



of this character is the presence of two separate barbels, 12 (Fig. 

 185). This supposition is supported ontogenetically by two ju- 

 venile Parexocoetus brachypterus brachypterus. The smaller one 

 (Fig. 182A, 18.1 mm) has a short beak from the ventral surface 

 of which a pair of small barbels develop in the larger one (Fig. 

 182B, 19.7 mm). Fusion into a single barbel (13) and secondary 

 loss of the barbels (14) are more derived states. Loss of the 

 barbels has apparently occurred independently in the three most 

 advanced subfamilies of the Exocoetidae. 



Scomberesocoidea 



The superfamily is defined by two derived characters: pres- 

 ence of a premaxillary canal, unique among teleosts; and upper 

 jaw at least slightly elongate. Other diagnostic characters in- 

 clude: third pair of upper pharyngeal bones separate, fourth 

 upper pharyngeal bone usually present, scales on body small. 

 The Scomberesocoidea differ from the Exocoetoidea in four 

 characters of the acoustico-lateralis system (Parin and Astak- 

 hov, 1982). The cephalic system is more complete in the Scom- 

 beresocoidea than in the Exocoetoidea. 



Scomberesocidae 



Defined by one derived character: dorsal and anal fins fol- 

 lowed by a series of finlets. Other diagnostic characters include: 

 upper and lower jaws only slightly elongate, teeth small; pectoral 

 branch of lateral line absent, posttemporal simple. There are 

 four more differences in the acoustico-lateralis system between 

 the Scomberesocidae and the Belonidae (Parin and Astakhov, 

 1982). 



Four monotypic genera were recognized by Hubbs and Wisner 

 (1980): Scomhereso.x and its dwarf derivative Nantchthys. and 

 Cololabis and its dwarf derivative Elassichthys. All sauries are 

 marine holoepipelagic fishes. Scomberesox reaches the largest 

 size, 450 mm SL, Nanichthys reaches 126 mm; Cololabis reaches 

 350-400 mm, Elassichthys only 68 mm. The two dwarf taxa 

 differ convergently from Scomberesox and Cololabis in losing 

 one ovary and the swimbladder and in having fewer vertebrae, 

 branchiostegal rays, pectoral fin rays, and gill rakers. Rather 

 than recognizing four monotypic genera, we recognize two evo- 

 lutionary lines in the family by considering Nanichthys as a 

 synonym of Scomberesox and Elassichthys a synonym of Col- 

 olabis as previously suggested by Parin (1968). 



Belonidae 



Defined by one derived reductive character: interruptions in 

 the cephalic lateralis system. Other diagnostic characters in- 

 clude: no finlets following dorsal and anal fins; both upper and 

 lower jaws usually elongate and studded with relatively large 

 sharp teeth; pectoral branch of lateral line present; posttemporal 

 forked. 



The Belonidae contain 10 genera and 32 species (Collette, 

 1966, 1974a, 1982a). Four genera are monotypic: the southern 

 African Petalichthys. the worldwide Ablennes and Platybelone. 

 and the Asian freshwater Xenentodon. Belone contains two east- 

 em Atlantic species. Three genera are restricted to freshwaters 

 of South America: Pseudotylosiirus (two species), Potamorrha- 

 phis (three), and Belonion (two). Tylosurus contains five species 

 of strictly marine species; Slrongylura 14 species, some marine, 

 some estuarine, and three strictly freshwater. 



The genera Belone and Petalichthys appear to be most gen- 



