The family Pimelodidae comprises some 300 species of Neotropical catfish organized in more than 60 nominal genera. The marked interspecific morphological variation in this family makes it difficult to explore the phylogenetic relationships among its subthaxons, which remain unexplored in the light of modern principles of zoological systematics. This work aimed at: reidentifying the Pimelodid assemblages from MPEG's collection; testing the hypothesis of subdivision of Pimelodidae into three subfamilies - Pimelodinae, Pseudopimelodinae, and Rhamdiinae (sensu Lundberg et al., 1991); and proposing a practical key for genera and species of Amazonian Pimelodids represented at MPEG. All specimens were submitted to morphometric and meristic treatment, and those suitable for osteological examination were dissected or prepared in alizarin. The various characters were compared to those established by Lundberg as diagnostic synapomorphies. These synapomorphies include, among others, the peculiar morphology of the lateral ethmoid, the suspensory and Weber's apparatus in each of the subfamilies. The present work also suggests the possibility of constituting an additional synapomorphy of Pimelodinae the bony platform formed by the parapophyses of vertebrae I to VI, which confines posteriorly the limits of the swim bladder. Despite the large geographic distance (denoting different populations) separating the species examined here from those previously studied in the literature, the results basically corroborated the subordination of the genera examined to the subfamilies in question. The identification key proposed here is pioneering in that it effectively employs characters observed in real specimens and not just based on previous literature descriptions.
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