Family Balitoridae Homalopteridae 107river loaches Freshwater Eurasia

Three or more pairs of barbels present near mouth.

Recognition of Nemacheilinae and Balitorinae as comprising a mono-phyletic lineage follows Sawada (1982). According to this author, balitorids may be recognized as a separate lineage from cobitids by differences in the Weberian apparatus (e.g., by the Y-shaped tripus, the most posterior element of the Weberian ossicles).

About 59 genera and about 590 species. The number of estimated valid species is approximate; there is much need for a systematic revision to determine how many nominal species are valid. Species are being described at a rapid rate and many undescribed species probably yet exist.

Subfamily Nemacheilinae. Prepalatine present; no spine under or before eye; two pairs of rostral barbels and one pair of maxillary barbels; body elongate, rounded, or compressed; mouth subterminal; single unbranched ray in pectoral and pelvic fins; adipose-like fin present in some; scales present or absent. Several cave species are known from Iran, India, China, Thailand, and Malaysia (e.g., Proudlove, 2005).

These loaches occur throughout much of Eurasia. Most species are in the India subcontinent, Indochina, and China.

At least 30 genera, e.g., Aborichthys, Acanthocobitis, Adiposia, Barbatula, Eonemachilus, Heminoemacheilus, Lefua,, Nemacheilus, Neonoemacheilus, Oreonectes, Orthrias, Paracobitis, Schistura (which contains the majority of species), Traccatichthys, Triplophysa, Vaillantella (the long-finned loaches with 50-60 dorsal fin rays and probably belonging in this subfamily), and Yunnanilus, with at least 420 species (e.g., Sawada, 1982; Kottelat, 1998, 2000a; Freyhof and Serov, 2001; Vishwanath and Laisram, 2001). Ellopostoma, of uncertain relationships, was placed in this subfamily by Tan and Lim (2002). Kottelat (1990a) gives a synonymy of the 31 named genera he recognized pending a phylogenetic study.

Subfamily Balitorinae (flat loaches). Exoccipitals separated from each other; interhyal absent; mesocoracoid fused with an enlarged cleithrum; three or more pairs of barbels present; gill opening restricted or not; paired fins enlarged with adhesive pads on ventral surface, orientated horizontally; pelvic fin separated or united under belly. These fishes, commonly known as the hill-stream loaches, have the body and head flattened, mouth subterminal, and paired fins adapted as adhesive organs. They are found in fast-flowing mountain streams from India through Southeast Asia including Sumatra, Java, and Borneo, to China and Taiwan.

In Nelson (1994) I recognized two tribes (that in earlier literature had been recognized as distinct at the family or subfamily level), the balitorines (= homa-lopterines) (with two or more unbranched anterior rays in both pectoral and pelvic fins) and gastromyzontines (single unbranched anterior ray in pectoral and pelvic fins). I now put all members together at the subfamily level only pending better cladistic resolution of relationships of the species.

About 29 genera, e.g., Annamia, Balitora (upper figure), Balitoropsis, Beaufortia,, Bhavania, Crossostoma, Cryptotora,, Erromyzon, Gastromyzon (lower figure), Glaniopsis, Hemimyzon, Homaloptera,, Katibasia,, LLepturichthys, Protomyzon, Sewellia, Sinogastromyzon, and Travancoria,, with at least 170 species (e.g., Tan and Martin-Smith, 1998; Freyhof, 2003; Freyhof and Serov, 2000; Kottelat, 1988, 1998, 2000a, 2001a,b, 2004b).

Order CHARACIFORMES (30)—characins. Teeth usually well developed (most are carnivores); adipose fin usually present; body almost always scaled (scales almost totally lacking in adults of the characid tetra Gymnocharacinus bergii of Argentina, which also lacks an adipose fin and is the most southerly known characiform); ctenoid or ctenoidlike scales in some; pelvic fin present (with 5-12 rays); anal fin short to moderately long (fewer than 45 rays); lateral line often decurved, sometimes incomplete; upper jaw usually not truly

protractile; pharyngeal teeth usually present, but not usually specialized as in cypriniforms (anostomids have highly modified pharyngeal teeth); barbels absent; branchiostegal rays 3-5; usually three postcleithra; first hypural separated from the centrum by a gap in adults (most other primitive teleosts lack such a gap); usually 19 principal caudal fin rays. Some characiforms lack the adipose fin (it may be present or absent among congeneric species). Maximum length about 1.4 m, attained by Hydrocynus goliath of the Congo. At the opposite extreme, many members are under 3 cm, and the smallest reach a maximum size of about 13 mm. Some members of this order are extremely colorful (many are silvery). Many species are popular aquarium fishes (often known as tetras). In South America, many are also important food fishes (e.g., Brycon).

The classification of this large assemblage of poorly known species, with much morphological diversity and where convergent evolution is common, has undergone much change as a result of the works noted below. However, there is the need for much more work to establish phylogenetic relationships. Fossils include Paleohoplias and Tiupampichthys from South America (Gayet et al., 2003), Eocitharinus (possibly in Citharinoidei) and Mahengecharax (and possibly sister to the Alestiidae) from Africa (Murray, 2003a, b), and Sorbinicharax (of the fossil family Sorbinicharacidae) (Taverne, 2003). Of particular interest, the early Cretaceous (Albion) Santanichthys of Brazil, although having two supramaxillary bones (unlike all other ostariophysans which lack the supramaxillary), is considered, with reservation, to be the oldest characi-form (and otophysan) and was probably either marine or brackish water (Filleul and Maisey, 2004). Phylogenetic concepts within this ordered are reviewed by Vari (1998).

Eighteen families with about 270 genera and at least 1674 species. All extant characins are confined to fresh water. At least 209 species occur in Africa, with the remainder in southwestern United States, Mexico, and Central and South America. The African members comprise three lineages—the citharinoids, the alestiids, and the one species of Hepsetus. As noted below, numbers of species for Central and South America taxa follow Reis et al. (2003); some species have been described after this work but are not given here.

The classification down to family level follows Buckup (1998) and that work should be consulted for details of the synapomorphies of the various clades. The family descriptions below do not necessarily give diagnostic features. This is the sister group to the remaining two orders (see above under Otophysi).

Suborder Citharinoidei. Teeth bicuspidate; second and third postcleithra fused; neural arch of fourth vertebra autogenous; premaxillary ascending process absent; scales ctenoid (cycloid in Citharinus); pelvic fin rays relatively numerous.

Fink and Fink (1981) and Buckup (1998) postulated this group to be the primitive sister group to all other characiforms, with Xenocharax being the most primitive member.

Twenty genera and about 98 species.

Family DISTICHODONTIDAE (108)—distichodontids. Freshwater, Africa.

Freshwater Aquarium Fish

There are two evolutionary grades. One consists of those members with non-protractile upper jaws, which are micropredators and herbivores; their body shape is variable, ranging from deep (as in upper figure) to shallow. The other consists of species with a movable upper jaw, which are carnivores, eating the fins of other fishes or the whole fish; their body is usually elongate (as in lower figure). This latter group was frequently recognized as a subfamily or family (Ichthyboridae). Maximum length 83 cm, attained in Distichodus niloticus.

Seventeen genera, Belonophago, Congocharax, Distichodus, Dundocharax, Eugnathichthys, Hemigrammocharax, Hemistichodus, Ichthyborus, Mesoborus, Microstomatichthyoborus, Nannaethiops, Nannocharax, Neolebias, Paradistichodus, Paraphago, Phago, and Xenocharax, with about 90 species (J. Daget and J. P. Gosse in Daget et al., 1984:184-211).

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