New Species of Hemigrammocharax (Characiformes: Distichodontidae) from the Northwestern Congo River Basin
Authors
Fernando C. Jerep1 and Richard P. Vari1
Abstract
Hemigrammocharax rubensteini is described from the northwestern Congo River basin in the Le´koli River of the Likouala River system, Republic of the Congo. The species differs from congeners in the combination of pigmentation pattern, meristics, and position of the dorsal fin. The presence of a well-developed pseudotympanum, a feature not previously reported in the Distichodontidae, is reported for H. rubensteini and other members of Hemigrammocharax and Nannocharax.
Fig. 1. Hemigrammocharax rubensteini, CU 89502, 23.6 mm SL, holotype; Africa, Republic of the Congo, Cuvette-Ouest, Likouala River drainage, Le´koli River at Mboko dock, Odzala National Park.
SPECIES of the genus Hemigrammocharax inhabit the streams and rivers of major portions of sub-Saharan Africa including the Congo, Cunene, Okavango, and Zambezi river basins (Poll, 1973; Daget and Gosse, 1984). Hemigrammocharax was proposed by Pellegrin (1923) to host Nannocharax ocellicauda, a species which although sharing the other diagnostic features of the species then assigned to Nannocharax, nonetheless lacked poring of the lateral line along the posterior portion of the body contra the completely pored lateral line in the other species of Nannocharax. As now defined, Hemigrammocharax consists of nine species diagnosed among the genera of the Distichodontidae by the presence of a single row of teeth on the dentary and premaxilla and incomplete poring of the lateral line. Hemigrammocharax is hypothesized to form a natural lineage with Nannocharax inside the family Dis- tichodontidae based on the common possession in those genera of a series of characters involving multiple body systems (Vari, 1979:331); however, the monophyly of Hemigrammocharax has yet to be assessed and indeed has been questioned (Vari and Ge´ry, 1981:1082). We describe a new species from the Likouala River basin, a tributary on the Congo River in the northwestern portion of the basin that conforms to the present concept of Hemigrammocharax and is assigned to that genus pending the results of ongoing phylogenetic analyses.
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