| The diversity of Pseudoplatystoma has been ambiguously estimated due to a lack of critical taxonomic and systematic studies. The genus displays extensive geographic variation in morphology and pigmentation that has been understudied in the past. Analysis and evaluation of these variations rendered a better estimation of the number of species of Pseudoplatystoma . A taxonomic revision is provided herein with description of three new species: P. orinoco, P. magdalenae, and P. metae ; and revalidation of P. punctifer and P. reticulatum. Consequently, the diversity of the genus changed from three recognized species to eight.; A comparative anatomical study of both P. fasciatum (type species), P. tigrinum (sensu stricto), and presumed related genera revealed 110 characters useful in phylogenetic analyses. Two lineages within Pseudoplatystoma were recovered: (1) the P. fasciatum group (P. reticulatum, P. orinoco, P. magdalenae, P. fasciatum, P. punctifer, and P. corruscans), and (2) the P. tigrinum group (P. metae, and P. tigrinum ). Bootstrap support was relatively high (79) for the P. fasciatum group and consistently high (100) for the P. tigrinum group. Relationships of Pseudoplatystoma and similar-appearing pimelodid genera, Sorubim, Sorubimichthys, Hemisorubim and Zungaro (=Paulicea) were also evaluated. The monophyly of these genera, including Pseudoplatystoma, has been estimated in the past and corroborated in this study. The basal position of Zungaro is consistently recovered in the three phylogenetic analyses. The genera Sombim, Sorubimichthys, Hemisorubim, and Pseudoplatystoma form a monophyletic lineage recovered in the three phylogenetic analyses. Sister relationships among these four genera remain inconclusive. However, the presence of the novel muscle retractor labiae in Sorubimichthys, Hemisorubim, and Pseudoplatystoma may resolve the conflict when a weight of 7 is conferred to this feature. The retractor labiae performs an important role in the life of these catfishes. Therefore, a higher weight was conferred to this feature, based on its complex functional anatomy.; An historical biogeographic analysis of the major South American rivers is also presented, based on combination of different individual biogeographic hypotheses. Four individual area cladograms based on previous phylogenetic studies of neotropical fishes were included in a preliminary analysis. Three general area cladograms were recovered using Nelson, Majority Rule, and Adams consensus options implemented by Component 2.0. Nelson and Majority Rule consensus trees were congruent; however, relationships of the Suriname River and Sao Francisco River with Amazon+Parana Rivers was uncertain. An Adams consensus tree was congruent with both Nelson and Majority Rule trees. For instance, trans-Andean (Magdalena+Atrato) and cis-Andean Rivers form monophyletic groups. A second historical biogeographic analysis was performed including the freshwater crab genus Dilocarcinus. It rendered a fully resolved general area cladogram. This biogeographic tree is congruent with some of the geologic events leading to the present day configuration of major South American River basins. |
