TFamily Araripichthyidae Position uncertain

Body deep; dorsal and anal fins with long base; pelvic fins and skeleton absent; pectoral fins attached low on body; caudal fin forked; teeth in jaws absent; pre-maxilla protractile and forming border of upper jaw; supramaxilla present; supraorbitals absent.

J. G. Maisey and S. Blum in Maisey (1991:208-15) note many similarities between this taxon and the lampriforms. However, they do not find evidence to support earlier suggestions that it is an acanthopterygian or a beryciform. They also cast doubt on original reports that it had spiny fin rays.

One genus, Araripichthys, marine, from the Lower Cretaceous in Brazil.

Leptocephalus larva (ribbonlike, totally unlike the adult); swim bladder not connected with ear (in Megalops, however, it does lie against the skull); no reces-sus lateralis; hypurals, when present, on three or more centra; branchiostegal rays usually more than 15; parasphenoid toothed (except in some notacan-thoids). During metamorphosis from the leptocephalus to the juvenile body form, the fish shrinks greatly in length. Larvae commonly reach 10 cm and may be as long as 2 m. Bohlke (1989, vol. 2) gave keys and descriptions for the lep-tocephali of this group.

Subdivision ELOPOMORPHA

Elopomorpha

Representatives of some elopomorph leptocephalus larvae. Typical maximum length given.

Elops 5 cm

Albula 6 cm notacanthid 1-2 cm ophichthid 12 cm saccopharyngoid 5 cm

Representatives of some elopomorph leptocephalus larvae. Typical maximum length given.

Some historical notes on the classification of the elopomorphs are given in Nelson (1994), and older classifications based on adult characters recognized markedly different relationships of the taxa given here. The relationship between the members of this group is based largely on the common occurrence of a leptocephalus larval stage. Not all authors accept the larva as a valid indicator of affinity. As with many fish taxa, there is controversy as to whether the elopomorphs are monophyletic or not and, if they are, as to what the interrelationships are. For example, rather than the leptocephalus larvae representing a derived condition, W. H. Hulet and C. R. Robins, in Bohlke (1989:669-77), believe it to be a primitive condition and therefore of limited systematic significance. Forey et al. (1996) concluded that elopomorphs and anguilliforms, as shown here, are monophyletic; their classification differs little from that herein. Recently, Filleul and Lavoue (2001) felt that the morphological characters used to support the monophyly of the Elopomorpha are mostly weak and proposed a new hypothesis of relationships based on nucleo-tidic sequences of ribosomal RNA 18S, 16S, and 12S. They concluded that the Elopomorpha are not monophyletic, and considered elopiforms, anguilliforms, albuliforms, and notacanthiforms as four monophyletic, incertae sedis taxa among basal teleosts. However, Wang et al. (2003), in an analysis of 12S rRNA sequences, confirmed a monophyletic Elopomorpha, and concluded that Elops and Megalops share a common ancestor and are clustered at the bottom of Elopomorpha, and that Albula and Notacanthus share a common ancestor forming the sister group to Anguilliformes, but that the Congroidei are not monophyletic and neither are the Anguilliformes without the Saccopharyngiformes. Inoue et al. (2004) also demonstrated the monopoly of the Elopomorpha. However, it is still possible that our concept of elopomorphs will change, or at least our view of interrelationships, when more morphological studies are done employing both fossil and extant taxa and more out-groups, combined with extensive molecular studies. However, for the present edition, I have made no higher-level changes from that given in Nelson (1994).

Of the fossil taxa, Eichstaettia and the possibly related Leptolepides (Arratia, 1991) may be the most primitive known elopomorph fossils. Other fossil elopomorphs not mentioned below include Anaethalionidae with Anaethalion (oldest record is Late Jurassic), Davichthys, Lebonichthys, and Brannerion and Osmeroides (both albuloids); these and others are reviewed by Forey et al.

Four orders, 24 families, 156 genera, and about 856 species. All but six species are marine or primarily marine.

Order ELOPIFORMES (23)—tenpounders. Pelvic fins abdominal; body slender, usually compressed; gill openings wide; caudal fin deeply forked; caudal fin with seven hypurals; scales cycloid; mesocoracoid and postcleithra present; gular plate well developed (median); branchiostegal rays 23-35; mouth bordered by premaxilla and toothed maxilla; upper jaw extending past eye; tip of snout not overhanging mouth (mouth terminal or superior) ; no sensory canal extending onto the small premaxilla. Leptocephali small, maximum length about 5 cm, with a well-developed, forked, caudal fin, a posterior dorsal fin (pelvic fins in older larvae), and about 53-86 myomeres (see D. G. Smith, pp. 961-72, in Bohlke, 1989).

Two families, two genera, and about eight species.

Family ELOPIDAE (69)—tenpounders (ladyfishes). Mainly marine (rarely brackish and freshwater); tropical and subtropical oceans.

Body rounded (little compressed); mouth terminal; pseudobranchiae large; branchiostegal rays 27-35; dorsal fin rays usually 20-25, the last ray not elongate; anal fin rays usually 13-18; pelvic rays usually 12-16, no conus arteriosus;

Pseudobranchiae

lateral line tubes unbranched; lateral line scales usually 95-120; insertion of pelvic fin beneath or posterior to origin of dorsal fin; vertebrae 63-79. Maximum length 1.0 m, attained in Elops machnata.

One genus, Elops, with about six species (e.g., Smith, 2003). The taxonomy of this genus is poorly known, and some authors recognize fewer species.

Family MEGALOPIDAE (70)—tarpons. Mainly marine (enters freshwater); tropical and subtropical oceans.

Freshwater Tropical Fish

Body compressed; mouth terminal or superior; pseudobranchiae absent; branchiostegal rays 23-27; dorsal fin rays 13-21, the last ray elongate; anal fin rays usually 22-29; pelvic rays 10 or 11; conus arteriosus present; lateral line tubes branched (radiating over surface of lateral line scales); only elopiform with the swim bladder lying against the skull (there is no intimate association between the swim bladder and the perilymphatic cavity as in clupeoids and notopteroids). Maximum length about 2.4 m, attained in Megalops atlanticus.

Two species, Megalops cyprinoides of the Indo-West Pacific (Africa to Society Islands) and Megalops atlanticus (= Tarpon atlanticus) of the western Atlantic (North Carolina, rarely north to Nova Scotia, to Brazil and offshore) and off tropical West Africa (rarely to southern Europe). The two species can be distinguished as follows:

Megalops cyprinoides. Insertion of pelvic fin beneath origin of dorsal fin; dorsal fin rays 17-21; lateral line scales 37-42; vertebrae 67 or 68; expanded arm of the intercalar forming the entire wall of the large periotic bulla. Megalops atlanticus. Insertion of pelvic fin in advance of origin of dorsal fin; dorsal fin rays 13-16; lateral line scales 41-48; vertebrae 53-57; intercalar does not form part of lateral wall of periotic cavity.

Order ALBULIFORMES (24)—bonefishes. Mandibular sensory canal lying in an open groove in the dentary and angular bones (in all other elopo-morphs the groove is roofed; in Albula there is a small roof in the angular). Three families, eight genera, and about 30 species.

Suborder Albuloidei. Body herringlike; gular plate reduced to a thin median splint or absent; pelvic rays 10-14; mouth bordered primarily by the premax-illa (maxilla toothed only in Pterothrissinae); upper jaw not extending as far as front of eye; tip of snout overhanging mouth (mouth inferior); caudal fin with six hypurals; infraorbital lateral line canal extending onto premaxilla, which is rare among living teleosteans; branchiostegal rays 6-16.

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