FOrder Lycopteriformes Incertae sedis

tFamily LYCOPTERIDAE. Upper Jurassic to Lower Cretaceous; freshwater; eastern Asia.

Includes the well-known genus Lycoptera. Li and Wilson (1996), on the basis of four synapomrphies, regarded the Lycopteridae as stem-group osteoglos-somorphs, sister to all extant clades. In what I regard as a minor difference, Hilton (2003) placed it incertae sedis, finding it to be either the sister group of all other osteoglossomorphs he sampled or of Eohiodon + Hiodon.

Order HIODONTIFORMES (21)—mooneyes. Placement of the Hiodontidae in its own order rather than in the Osteoglossiformes, as formerly done (Nelson, 1994), follows Li and Wilson (1996) and Hilton (2003).

Family HIODONTIDAE (64)—mooneyes. Freshwater; North America (primarily Mackenzie, Saskatchewan, Mississippi, and St. Lawrence river systems).

Anal fin moderately long (23-33 rays) and not confluent with the well-developed forked caudal fin; pelvic fins distinct, with seven rays; 7-10 branchiostegal rays; subopercular present; lateral line scales about 54-61. Length up to 51 cm.

Two species: Hiodon tergisus (Mooneye) with 11 or 12 principal dorsal fin rays and ventral keel not extending in front of pelvic fins; and Hiodon alosoides (Goldeye) with 9 or 10 principal dorsal fin rays and ventral keel extending in front of pelvics.

Several species of the fossil Eohiodon are known from Eocene deposits in western North America. Other fossil hiodontid genera are Plesiolycoptera and Yanbiania of the Cretaceous of China (Li and Wilson, 1996; Li et al., 1997).

Order OSTEOGLOSSIFORMES (22)—bonytongues. Intestine passes posteriorly to left of esophagus and stomach; parasphenoid and tongue bones usually with well-developed teeth and forming a shearing bite (mesopterygoid and usually the ectopterygoid also toothed); premaxilla small and fixed to the skull; no supramaxilla; caudal fin skeleton with large first ural centrum and no uro-dermals, one or more epurals fused with uroneurals; caudal fin with 16 or fewer branched rays; nasal capsule rigid, no antorbital-supraorbital system for pumping water over olfactory epithelium; epipleural intermuscular bones absent; one or two pyloric caeca, one caecum in Pantodon and two in other osteoglossiforms.

Two monophyletic clades are recognized—the osteoglossoids and the notopteroids. Evidence, summarized in Lauder and Liem (1983), that the Osteoglossinae and Pantodon form a monophyletic clade and that the notopterids and mormyroids form a monophyletic clade was confirmed by Li and Wilson (1996) and is accepted here.

The osteoglossomorph Ostariostoma from Upper Cretaceous or lower Paleocene freshwater deposits of Montana assigned to the family Ostariostomidae was placed by Li and Wilson (1996) in their suborder Notopteroidei (they provisionally also included the Paleocene Thaumaturus), but found to be the sister group of all non-hiodontiform osteoglossomorphs by Hilton (2003). Subsequently, the latter position was accorded to the Early Cretaceous Xixiaichthys from China by Zhang (2004). The Cretaceous Palaeonotopterus from Morocco was considered to be related to either mormyrids or notopterids by Cavin and Forey (2001) (however, a 2004 paper by L. Taverne suggests that more phylogenetic work is needed before we can be confident of relationships).

The phylogeny of Li and Wilson (1996) suggested that in classification the Osteoglossidae be placed in the suborder Osteoglossoidei, and that Notopteridae, Mormyridae, and Gymnarchidae be placed in the suborder Notopteroidei. However, Hilton (2003) found that mormyrids are the sister group of notopterids + osteoglossids. I have not used the categories of suborder or superfamily to express relationships.

Four families, 28 genera, and about 218 species. All species occur in freshwater; only some notopterids enter brackish water.

Family OSTEOGLOSSIDAE (65)—osteoglossids or bonytongues. Freshwater; circum-tropical, South America, Africa, and Southeast Asia to northern Australia.

Maxilla toothed; no intracranial penetration of swim bladder; six pelvic rays; pelvic fins distinctly behind base of pectoral fins; some possess a suprabranchial organ and can utilize atmospheric air; lateral line scales 21-55; 60-100 vertebrae.

Most osteoglossids are omnivorous or carnivorous.

Five genera and eight species. A number of fossils are recognized: e.g., Phareodus from the Eocene of Wyoming, and Brychaetus of the Paleocene and Eocene of Europe and Africa. Additional fossils are given in Li and Wilson (1996), Hilton (2003), and Zhang (2004).

Subfamily Heterotidinae. No mandibular barbels; branchiostegal rays 10 or 11 (Arapaima) or 7-9 (Heterotis).

Ostariostomidae

Two species, Arapaima gigas (Pirarucu) of South America (upper figure) and Heterotis niloticus, which lacks parasphenoid teeth and has reduced tongue teeth, of western Africa (lower figure above). A. gigas of South America, one of the world's largest species of scaled freshwater fish, grows to about 2-2/2 m in length, although larger specimens probably existed before the modern fisheries. Heterotis niloticus, which grows to 98 cm in length, has a unique spiralled epibranchial organ that aids in concentrating and swallowing food.

Subfamily Osteoglossinae. Osteoglossum and Scleropages have mandibular barbels present; 10-17 branchiostegal rays.

Osteoglossum bicirrhosum (silver aruana, arowana, or arawana) and O. ferreirai (Black Aruana) of South America have 42-57 dorsal fin rays.

Scleropages jardinii of northern Australia and New Guinea, S. leichardti of the Fitzroy River in Queensland, Australia, and S. formosus of Southeast Asia

(including Sumatra and Borneo) have about 20 dorsal fin rays. Three other valid species may constitute S. formosus and have been formally described by Pouyaud et al. (2003).

Pantodon buchholzi (Butterflyfish, shown above) of tropical western Africa, formerly recognized in its own family, Pantodontidae, has pelvic fins located under the pectoral fins; swim bladder that can act as an air-breathing organ; eight branchiostegal rays; greatly enlarged pectoral fins; suboperculum absent; interoperculum sometimes absent; 30 vertebrae. Length up to 10 cm.

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