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ABSTRACT A new species of Phenacogaster is described from the rio Salitre, a tributary of the lower middle rio São Francisco drainage. The new species can be clearly distinguished from all its congeners in having a conspicuous, broad caudal peduncle spot reaching the upper and lower margins of the peduncle with a short extension onto the middle caudal fin rays and another weaker extension over the lower lobe of the caudal fin.

ABSTRACT A new species of Astyanax belonging to the Astyanax scabripinnis complex is described from dos Touros River, tributary of the Pelotas River, Uruguay River basin. Astyanax taurorum sp. nov. is distinguished from other species of the Astyanax scabripinnis species complex by having two humeral spots, the first vertically elongated; teeth of inner row of premaxilla with three to five cusps; 2-3 (modes 2 or 3) maxillary teeth; 20-23 (mode 22) branched anal-fin rays; 13-15 (mode 14) gill rakers on lower branch of the first branchial arch; 20-23 (mode 21) total gill rakers in first branchial arch; 33-36 (mode 35) perforated lateral line scales. Astyanax taurorum sp. nov. is similar to Astyanax paris; nevertheless, it can be readily distinguished from it by having a smaller head depth (73.6-83.1% vs. 86.4-95.6%) and smaller interorbital width (24.1-28.0% vs. 30.8-32.8%). In addition, it differs from A. paris by the presence a posttemporal hook-shaped posterodorsal margin.

Nine new species of Phenacogaster Eigenmann, 1907 are described: Phenacogaster capitulatus sp. nov. from the Neshuya River system, Ucayali River basin; Phenacogaster maculoblongus sp. nov. from the upper Cuyuni River, and tributaries of the lower Orinoco River; Phenacogaster napoatilis sp. nov. from the Napo River system, upper Amazon River basin; Phenacogaster ojitatus sp. nov. from the Xingu River system; Phenacogaster prolatus sp. nov. from the Orinoco River, canal Casiquiare and upper and middle Negro River; Phenacogaster retropinnus sp. nov. from the Negro, Madeira and Xingu river systems; Phenacogaster simulatus sp. nov. from the Potaro River, Essequibo drainage; Phenacogaster wayampi sp. nov. from the Oiapoque River, and Phenacogaster wayana sp. nov. from the Corantijn (Suriname), Maroni, Mana, Sinnamary and Approuague rivers (French Guiana). The geographic distribution of P. megalostictus, previously recorded for the Negro River, Amazon River system, is restricted to the Essequibo River system, Guiana. The distribution of P. carteri, previously known only from the type-locality (Cuyuni River, Guyana), is extended to the lower Orinoco River. The reduction of the latero-sensory canal, mentioned in the literature as an autapomorphy for P. tegatus was observed in three additional species of Phenacogaster. The posterior humeral spot, found only in P. tegatus, is herein considered autapomorphic for the species. Diagnoses are given for previously described species based on the analysis of type material and additional specimens, and a key to the species of the genus is provided.