Fishes: A Guide to Their Diversity. Philip A. Hastings
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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 well over 2 m in length and are predatory, feeding primarily on fishes and invertebrates. They are able to respire via air gulped at the surface and passed into the physostomous gas bladder (Graham, 1997). There are two known species, one in the Atlantic and a second in the Indo-West Pacific. They are very popular sport fishes.
REFERENCES: Ault, 2008; Forey et al., 1996; Graham, 1997; Greenwood, 1970b; Seymour et al., 2008; Smith, in Carpenter, 2003; Wade, 1962.
MEGALOPID CHARACTERISTICS:
1) body elongate, laterally compressed
2) last ray of single dorsal fin elongate
3) mouth terminal to superior, large, extending past eye
4) pelvic fins abdominal
5) caudal fin deeply forked
6) single gular plate
7) scales large, less than 50 in lateral line
ILLUSTRATED SPECIMEN:
Megalops atlantica, SIO 78–124, 270 mm SL
ALBULIFORMES—Bonefishes
This group includes two families, the Albulidae (covered below) and the Pterothrissidae, two genera, and about 13 species. They are silvery fishes with a forked caudal fin in adults as well as in their leptocephalus larvae (also found in the Elopiformes) and are distinctive in a few osteological features (Forey et al., 1996; Wiley and Johnson, 2010).
REFERENCES: Forey et al., 1996; Wiley and Johnson, 2010.
ALBULIFORMES : ALBULIDAE—Bonefishes
DIVERSITY: 1 genus, 11+ species
REPRESENTATIVE GENUS: Albula
DISTRIBUTION: Atlantic, Indian, and Pacific oceans
HABITAT: Marine, occasionally in freshwater; tropical to warm temperate; coastal, demersal over soft bottoms
REMARKS: Bonefishes are coastal fishes characterized by their single dorsal fin, deeply forked caudal fin, and inferior mouth. As indicated by their mouth position, these fishes feed on or near the bottom, on crustaceans and other small invertebrates, as well as fishes. Reaching a maximum size of over 1 m, bonefishes are highly regarded as sport fishes, but are rarely eaten and generally not targeted commercially. Recent researchers have used molecular and morphological characters to determine the presence of several cryptic species (e.g., Hidaka et al., 2008; Pfeiler et al., 2008).
REFERENCES: Ault, 2008; Hidaka et al., 2008; Pfeiler et al., 2008; Smith, in Carpenter, 2003.
ALBULID CHARACTERISTICS:
1) body elongate
2) mouth inferior, small, not extending past eye
3) tail deeply forked
4) single gular plate
5) six to sixteen branchiostegal rays
6) scales small
ILLUSTRATED SPECIMEN:
Albula sp., SIO 62–213, 159 mm SL
NOTACANTHIFORMES—Spiny Eels and Halosaurs
DIVERSITY: 2 families, 6 genera, 27 species
REPRESENTATIVE GENERA: Aldrovandia, Halosaurus, Lipogenys, Notacanthus
DISTRIBUTION: Atlantic, Indian, and Pacific oceans
HABITAT: Marine; tropical to temperate; lower continental shelf to abyssal plain, demersal over soft bottoms
REMARKS: Spiny eels (Notacanthidae) and halosaurs (Halosauridae) are elongate, deepsea fishes that, in addition to the features below, are characterized by a large connective tissue nodule intercalated between the pterygoid arch and the maxilla. Their long anal fin extends nearly half the body length and includes numerous spines. Spiny eels and halosaurs associate with the benthos and feed on small invertebrates (e.g., crustaceans, echinoderms, polychaetes) and detritus. These fishes can regenerate their long tails when broken or injured. The leptocephalus larvae of some notacanthids are known to reach an amazing length of 2 m (Böhlke, 1989).
REFERENCES: Böhlke, 1989; Crabtree et al., 1985; Forey et al., 1996; Smith, in Carpenter, 2003; Sulak et al., 1984.