brackish water and feed on other fishes, some benthic invertebrates, and waterfowl. Several small, toothed bones (including the infraorbitals) form the upper jaw. Gars use their lung-like gas bladders to supplement respiration (Graham, 1997) and are known to spend time in a stationary position near the surface. Opisthocoelous vertebrae (anterior end convex, posterior end concave) are unique to this group, one genus of the Blenniidae, and some reptiles.
REFERENCES: Boschung and Mayden, 2004; Graham, 1997; Grande, 2010; Wiley, 1976; Wiley, in Carpenter, 2003.
LEPISOSTEIFORM CHARACTERISTICS:
1) elongate jaws with fanglike teeth
2) bony, ganoid scales in oblique rows
3) row of median scales along the first ray of the dorsal, anal, and caudal fins
4) body elongate, with the dorsal and anal fins located posteriorly
5) pectoral fins low on body, pelvic fins abdominal
6) cheek with numerous bony plates
7) three branchiostegal rays
ILLUSTRATED SPECIMEN:
Atractosteus spatula, TU 124963, 666 mm TL (lateral and dorsal views)
AMIIFORMES : AMIIDAE—Bowfins
DIVERSITY: 1 family, 1 genus, 1 species
REPRESENTATIVE GENUS: Amia
DISTRIBUTION: Eastern North America
HABITAT: Freshwater in streams, rivers, and swamps; temperate; demersal over soft bottoms
REMARKS: The Bowfin, Amia calva, is the only living representative of the Amiidae and Amiiformes. It is restricted to eastern North America, though fossil forms are known worldwide (Grande and Bemis, 1999). It inhabits still or slow-moving freshwaters and can swim by either undulating its long dorsal fin or utilizing its strong tail. The Bowfin is predatory and feeds on other fishes, reptiles, amphibians, birds, snails, and crayfishes. It is among the many groups of air-breathing fishes and utilizes its lung-like gas bladder to supplement respiration (Graham, 1997). Males construct a nest where they defend eggs and young after they hatch.
REFERENCES: Boschung and Mayden, 2004; Graham, 1997; Grande and Bemis, 1998, 1999.
AMIIFORM CHARACTERISTICS:
1) body cylindrical, with long dorsal fin
2) single gular plate
3) caudal fin heterocercal
4) ten to thirteen flattened branchiostegal rays
5) maxilla included in gape
6) males with prominent ocellus near upper base of caudal fin
ILLUSTRATED SPECIMEN:
Amia calva, SIO 69–491, 138 mm TL
INSET: Head of Amia calva, SIO uncatalogued (ventral view)
TELEOSTEI—Teleosts
The Teleostei has long been recognized as a monophyletic group. Its composition, distinctive features, and relationships have been discussed at length by a variety of authors (e.g., Arratia, 1997, 1999, 2001; de Pinna, 1996; Fujita, 1990; Gosline, 1971; Greenwood et al., 1966; McAllister, 1968; Nelson et al., 2010; Patterson and Johnson, 1995; Wiley and Johnson, 2010; Winterbottom, 1974a). Most extant members have a somewhat to highly mobile premaxilla that is free from the skull, unpaired basibranchial tooth plates, a unique caudal-fin skeleton with elongate uroneurals (modified neural spines), and a number of other features. The extraordinary diversification of the teleosts has been attributed, in part, to a genome duplication event that occurred early in their evolution (Hoegg et al., 2004; Hurley et al., 2007; Meyer and Van de Peer, 2005; Santini et al., 2009). The diversity of the Teleostei is immense, including approximately 96% of all living “fish” species (Nelson, 2006). Several recent studies (e.g., Betancur et al., 2013; Faircloth et al., 2013; Inoue et al., 2001; Ishiguro et al., 2003; Near et al., 2012, 2013) have hypothesized the relationships among the major lineages of teleosts based on molecular data.
Hypothesized phylogenetic relationships of the early lineages of the Teleostei. The traditional hypothesis (left), based on morphology (Nelson, 2006) and supported by Inoue et al. (2003), differs from the recent molecularly based hypothesis (right) of Faircloth et al. (2013) and Chen et al. (2014) in the placement of the Osteoglossomorpha and Elopomorpha.
OSTEOGLOSSOMORPHA—Bonytongues and Mooneyes
The bonytongues and relatives are a broadly distributed early lineage of ray-finned fishes with a substantial fossil record. Their evolution predates the breakup of Gondwana, with extant representatives found in freshwaters of North America, South America, Africa, Asia, and Australia. At least one group, the Notopteridae or Old World knifefishes, also occurs in brackish waters. They are characterized by several internal features (Hilton, 2003; Li and Wilson, 1996; Wiley and Johnson, 2010; Wilson and Murray, 2008) including a unique “shearing bite” between the basihyal and lateral pterygoquadrate teeth (Greenwood et al., 1966). Most species in the group provide parental care to eggs, and in some cases, young (Britz, 2004). Two lineages are recognized within the Osteoglossomorpha: the Osteoglossiformes, with four families (Mormyridae, or elephantfishes, Notopteridae, or Old World knifefishes, Osteoglossidae, or bonytongues, and Gymnarchidae, or African knifefishes), and the Hiodontiformes, with a single family (Hiodontidae, or mooneyes).
OSTEOGLOSSIFORMES—Bonytongues
DIVERSITY: 4 families, 28 genera, 234 species
REPRESENTATIVE GENERA: Arapaima, Chitala, Gymnarchus, Mormyrus, Pantodon
DISTRIBUTION: Circumtropical
HABITAT: Freshwater, rarely brackish, rivers, streams and still waters; tropical; near surface and over soft bottoms
REMARKS: The bonytongues exhibit remarkable variety in form among and within the four included families. The Osteoglossidae can have long dorsal and anal fins and attain a length of more than 2.5 m (Arapaima gigas) or have short dorsal and anal fins with a maximum length of 10 cm (Pantodon buchholzi). The long pectoral fins of P. buchholzi (Freshwater Butterflyfish) allow it to glide over the surface up to 2 m. The Notopteridae have an extremely long anal fin, but a short or absent dorsal fin, and the pelvic fins may be present or absent. The Mormyridae have moderately long dorsal and anal fins, considerable variation in the snout and lower jaw, and in some cases, electric organs. The monotypic Gymnarchidae (Gymnarchus niloticus) has no anal, pelvic, or caudal fins, but also has electric organs. Air breathing has been documented in all four families (Graham, 1997).
REFERENCES: Graham, 1997; Hilton,
