A Taxonomic Reconsideration of the Haplochromine Genera Gaurochromis Greenwood, 1980 and Labrochromis Regan, 1920 (Pisces, Cichlidae)

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Abstract
The insectivorous-molluscivorous haplochromine species belonging to the genera Gaurochromis Greenwood, 1980 and Labrochromis Regan, 1920 have been analysed. The degree of hypertrophy of the lower pharyngeal jaw, the apomorphic character for Labrochromis, is quantified and its intra-, interspecific and generic variability has been determined. Some measures for oral jaw-shape are given and the value of these for generic distinction is considered. In most, including apomorphic, characters L.ptistes overlaps with Gaurochromis and with other Labrochromis species. The overlap with the former genus is greater than that with the rest of the species of the genus in which it was placed by GREENWOOD (1980). L. humilior as described by GREENWOOD (1960), is a poly-specific taxon. The major part of the material is a-typical and belongs to a species which resembles an undescrib- ed species from the HEST-collections. Together this material may bridge the gap bet- ween Gaurochromis and Enterochromis. The types of L. humilior deviate from Gaurochromis and Labrochromis in several aspects. The subgenera G. Gaurochromis and G. Mylacochromis are invalidated by G. iris and G. hiatus which fully bridge the subgeneric "gap". It is demonstrated that Gaurochromis plus Labrochromis species can be placed in con- tinuous morphoclines on the basis of different characters, which include the apomor- phic ones supposedly defining the seperate lineages. The only characters that show some discontinuity are oral jaw-lengths combined with head-length. However, oral and pharyngeal jaw-development are correlated and are shown to co-vary in- traspecifically, so that the value for generic distinction is doubted. The problem of classification of haplochromines is discussed and the use of statistical methods such as principal component analysis is suggested. A conventional cladistic approach is not easily applicable in groups such as these lacustrine haplochromines

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