Review of the genus Hypostomus Lacépède, 1803 from rio Ribeira de Iguape basin, with description of a new species (Pisces, Siluriformes, Loricariidae). Osvaldo T. Oyakawa Alberto Akama Angela M. Zanata Zootaxa 2005 921 1 27 52WZ 36713 urn:lsid:zoobank.org:act:E0BC8DAD-9CD9-4E32-920A-063D33AD0E80 Loricariidae Hypostomus CoL Animalia Hypostomus Lacépède 1803:144 Siluriformes 23 Chordata genus  Discussion Four nominal species of Hypostomusare cited in the literature for rio Ribeira de Iguape basin: Hypostomus agna (Miranda-Ribeiro, 1907), Hypostomus commersonii Valenciennes, 1840, Hypostomus interruptus (Miranda-Ribeiro, 1918), and Hypostomus lacerta (Nichols, 1919). Hypostomus lacertawas recently transferred to the genus Kronichthysby Armbruster& Page (1997). Hypostomus commersoniiwas described for the La Plata river basin, Uruguay, and to rio SaoFrancisco, Brazil. Subsequent authors registered the species in other Brazilian drainages (e.g., rio Paraibado Sul (Steindachner, 1876; MirandaRibeiro, 1911, 1918), rio Parana(Miranda-Ribeiro, 1911), and rio Ribeira de Iguape (Miranda-Ribeiro, 1907, 1908a, b, 1918)), broadening the distribution of H. commersonii. Weber (1986), on the contrary, restricted the area of occurrence of H. commersoniito the La Plata river system and Mazzoni et al. (1994) corroborated the absence of this species in the rio Paraibado Sul drainage. Similarly, we herein confirm the absence of H. commersoniiin the Ribeira de Iguape river system. Our analysis revealed that the loricariids collected in the Ribeira do Iguape basin and previously identified in the literature as H. commersonii, have several distinctive features when compared to the La Plata river form. In fact, this material represents a new species and is described herein as H. tapijara, sp. n.Besides having a relatively distinct overall body form, H. tapijaracan be also distinguished from H. commersoniion the basis of several characters including the presence of larger and more numerous dark spots distributed over body and fins, and absence of oblique inconspicuous bands over flanks. These two species can be further distinguished from each other by the relatively higher degree of development of ridges and keels in H. commersonii.  Asnoted in the ‘Introduction’ some authors provided regional revisions of the genus Hypostomus. From those revisions, only Mazzoni et al. (1994) examined species from eastern Brazilian basins, recognizing only two valid species for lower portion of rio Paraibado Sul basin: Hypostomus affinis (Steindachner, 1877)and Hypostomus auroguttatus Kner, 1854, senior synonym of H. luetkeni (Steindachner, 1877)(see Weber, 2003:356). According to Mazzoni et al. (1994) both species are only in the rio Paraibado Sul or northern Brazilian drainages. Furthermore, those species were not cited in the literature for the rio Ribeira de Iguape basin. Examination of specimens of H. affinisin the present study revealed some similarities in coloration with H. interruptusand H. tapijara. However, H. affinishave body comparatively more elongated than H. interruptusand also have larger and more conspicuous dark spots distributed over body and fins (compare Fig. 6 with fig. 2 of Mazzoni et al., 1994). Hypostomus affinisdiffers from H. tapijaraby the absence of broad dorsal fin and absence of strongly developed keels characteristic of the later species (compare Fig. 7 with fig. 2 of Mazzoni et al, 1994). According to Bizerril (1994), there is another species from rio Paraibado Sul basin, H. punctatus, which belongs to the H. commersonigroup, and can be readily distinguished from H. tapijaraby having smaller spots over body and fins, four dark brown inconspicuous oblique bands, absence of a broad dorsal fin and body not so elongated. In the case of Hypostomus auroguttatus, comparisons with species of Hypostomusfrom rio Ribeira de Iguape basin revealed several similarities with H. agna, mainly related to the body shape, alignment of series of plates in anterior and posterior portion of trunk, absence of keels, and coloration (compare Fig. 2 with fig. 3 of Mazzoni et al, 1994).   Although H. agnais endemic to the rio Ribeira de Iguape system (Weber, 2003:355) and H. auroguttatuswas never reported in the literature to occur in this river basin, the distinction between the two species based on the examination of the available material of both species is apparently problematic. In fact, taxonomic difficulties involving H. auroguttatuswere previously emphasized by Weber (2003:364), under his comments of Hypostomus vermicularis (Eigenmann & Eigenmann). According to the author, H. vermicularisneeds a revision, a task beyond the scope of this study. Considering the known geographic distribution of H. auroguttatus, the undoubted presence of H. agnain rio Ribeira de Iguape basin and the limited focus of the present study we defer to propose a synonymization of these two species and maintain H. agnaas the species present in the rio Ribeira de Iguape basin. Thus the four species found to occur in rio Ribeira do Iguape basin includes those two previously cited in the literature and confirmed to be present in this study, recognized as H. agnaand H. interruptus, one species recorded for the first time in this system that is Hypostomus ancistroides, and the new species H. tapijara.