Li et al., 1997; Wilson and Murray, 2008; Zhang, 2006.
OSTEOGLOSSIFORM CHARACTERISTICS:
1) glossohyal (tongue bone) usually with teeth
2) pelvic fins abdominal or (rarely) absent
3) premaxilla fixed to skull
4) branched caudal-fin rays usually fewer than 16
5) three to seventeen branchiostegal rays
6) six (or fewer) hypurals
ILLUSTRATED SPECIMENS:
A) Arapaima gigas, SIO 76–343, 809 mm SL (Osteoglossidae—bonytongues)
B) Gnathonemus petersii, SIO 64–228, 118 mm SL (Mormyridae—elephantfishes)
C) Xenomystus nigri, SIO 64–228, 132 mm SL (Notopteridae—featherfin knifefishes)
D) Gymnarchus niloticus, SIO 64–228, 165 mm SL (Gymnarchidae—Aba or African Knifefish)
HIODONTIFORMES : HIODONTIDAE—Mooneyes
DIVERSITY: 1 family, 1 genus, 2 species
REPRESENTATIVE GENUS: Hiodon
DISTRIBUTION: North America
HABITAT: Freshwater; temperate; pelagic in slow-moving rivers and lakes
REMARKS: Mooneyes characteristically have large eyes, their diameter greater than the length of the snout, and silvery or golden bodies. Unlike similar families, in mooneyes the single dorsal fin is located well posterior to the origin of the abdominal pelvic fins. Mooneyes migrate either upstream or to lake shallows in order to spawn. These fishes are visual predators and feed near the surface at night and during low light, primarily on insects, crustaceans, small fishes, frogs, and small mammals. The anal fin is sexually dimorphic, with males having thickened anterior rays.
REFERENCES: Boschung and Mayden, 2004; Britz, 2004; Greenwood, 1970a; Hilton, 2003; Li and Wilson, 1994; Li et al., 1997.
HIODONTIFORM CHARACTERISTICS:
1) single, short-based dorsal fin situated relatively far posteriorly
2) anal-fin base much longer than dorsal-fin base
3) subopercle with a small spine
4) seven to ten branchiostegal rays
5) pelvic fins with seven rays
6) eyes large
ILLUSTRATED SPECIMEN:
Hiodon tergisus, SIO 74–131, 99 mm SL
ELOPOMORPHA
This large group of morphologically diverse fishes is united in sharing a distinctive larval type, the leptocephalus. These ribbon-shaped larvae have small heads and elongate bodies that in some may be as long as 2 m (Böhlke, 1989). At metamorphosis, they shrink in size and take up the general form of their respective lineages. In addition, elopomorphs have numerous branchiostegal rays (15 or more) and teeth on the parasphenoid. The group includes over 850 species classified in five orders, 24 families, and 156 genera. The largest of these orders is the Anguilliformes or true eels, with nearly 800 species. While the monophyly of the Elopomorpha has been questioned by some, recent molecular data and morphological evidence support its monophyly (Chen et al., 2014; Forey, 1973; Forey et al., 1996; Inoue et al., 2004; Obermiller and Pfeiler, 2003; Wiley and Johnson, 2010).
Hypothesized phylogenetic relationships of the Elopomorpha after Chen et al. (2014); that study placed the Saccopharyngiformes within the Anguilliformes.
ELOPIFORMES—Tenpounders and Tarpons
Members of Elopiformes have an elongate body, abdominal pelvic fins, long jaws with toothed premaxillae and maxillae in the gape, wide gill openings, a single gular plate, cycloid scales, and numerous (23–35) branchiostagal rays. Like those of the Albuliformes, their leptocephali have a well-developed, forked caudal fin. This group includes two families, the well-known tarpons (Megalopidae) and the tenpounders (Elopidae).
ELOPIFORMES : ELOPIDAE—Tenpounders and Ladyfishes
DIVERSITY: 1 genus, 7 species
REPRESENTATIVE GENUS: Elops
DISTRIBUTION: Atlantic, Indian and Pacific oceans
HABITAT: Primarily marine but occasionally in brackish estuaries and freshwater; tropical to subtropical; coastal pelagic
REMARKS: Tenpounders are elongate, silvery fishes with a large, terminal mouth and a deeply forked caudal fin. These predatory fishes reach lengths of approximately 1 m and feed primarily on small fishes and some crustaceans. Unlike the closely related tarpons, tenpounders do not breathe air but do possess a large pseudobranch. There are currently only seven described species of tenpounders, but there are likely more undescribed, cryptic species in the Indo-Pacific and elsewhere (McBride et al., 2010). Tenpounders are generally not targeted commercially but are considered a good sport fish.
REFERENCES: McBride et al., 2010; Smith, in Carpenter, 2003; Whitehead, 1962.
ELOPID CHARACTERISTICS:
1) body elongate and somewhat rounded in cross section
2) last ray of single dorsal fin not elongate
3) mouth terminal, large, extending past eye
4) pelvic fins abdominal
5) caudal fin deeply forked
6) single gular plate
7) scales small, approximately 100 in lateral line
ILLUSTRATED SPECIMEN:
Elops affinis, SIO 64–326, 172 mm SL
ELOPIFORMES : MEGALOPIDAE—Tarpons
DIVERSITY: 1 genus, 2 species
REPRESENTATIVE GENUS: Megalops
DISTRIBUTION: Atlantic and Indo-West Pacific oceans
HABITAT: Primarily marine but occasionally in brackish estuaries and freshwater; tropical to subtropical; coastal pelagic
REMARKS: The tarpons are large, silvery fishes with large scales, a slightly superior mouth, and a deeply forked caudal fin. They grow to
