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A systematic revision of the Neotropical catfish genus


(Teleostei, Pimelodidae)

Anders Silfvergrip


SILFVERGRIP, A.M.C. 1996. A systematic revision of the Neotropical catfish genus Rhamdia (Teleostei, Pimelodidae). Department of zoology, Stockholm University and Department of Vertebrate Zoology, Swedish Museum of Natural History, Stockholm. 156 pp. + 8 pls.

This monograph is a revison of the species of the genus Rhamdia, a genus of pimelodid catfishes with about 100 described species. The results, based on an evaluation of characters previously used in literature, show that morphological variation is great and that only few of the nominal species remain diagnosable. The valid species are:
Rhamdia foina (Müller & Troschel)
R. humilis (Günther)
R. itacaiunas n.sp.
R. jequitinhonha n.sp.
R. laticauda (Kner)
R. laukidi Bleeker
R. muelleri (Günther)
R. nicaraguensis (Günther)
R. poeyi Eigenmann & Eigenmann
R. quelen (Quoy & Gaimard)
R. xetequepeque n.sp.
The work includes several lecto- and neotype designations. The internal morphology of Rhamdia quelen, the type species of Rhamdia, is described to provide a basis for comparative work. The two main reasons for variation in body proportions are size allometry and a phenomenon here called the "Segmental effect". The Segmental effect represents an elongation of body proportions posterior to the head, in fish with many vertebrae, which puts constraints on the use of body proportions in phylogenetic analyses. Previous opinions on relationships of Rhamdia are reviewed and in part considered inconclusive because of their use of data which included body proportions with unsatisfactory reference distances.

Abstract © 1996 Anders Silfvergrip; reproduced with permission

On May 3, 1996, Anders Silfvergrip defended his doctoral thesis with the above title at the Swedish Museum of Natural History. Opponent was Mário de Pinna from São Paulo, Brazil. The thesis was passed without any problem. The thesis is published in conformation with the ICZN and names therein are available.