Agradecimentos: Type material of Hyphessobrycon montagi was collected during a biological survey funded by Alcoa Alumínio S/A (agreement Alcoa/MPEG/FIDESA). For help during fieldwork, we thank Alberto Bezerra, Luciano F.A. Montag, Marina Mendonça, Roberta Raiol, Alexandre Hercos, Roberta D. Silva, Guilherme Dutra, Luiz A.W. Peixoto, and Arthur B. Araújo. Travels to Belém by the first author were funded by the Programa de Pesquisa em Biodiversidade (PPBIO) from the Ministério da Ciência e Tecnologia (MCT), Brazilian government, and Programa Calha-norte (Conservation International, Brazil/MPEG/Sema). We are grateful to Lúcia H. Rapp Py-Daniel, Renildo R. de Oliveira, and Priscila M. Ito (INPA), Carlos A.S. Lucena and Zilda M.S. Lucena (MCP), and Osvaldo T. Oyakawa, Mario C.C. de Pinna, Manoela Marinho, and Michel D. Gianetti (MZUSP) for help while visiting their collections and for the loan of comparative material. Figures 1a-c were taken by Eduardo G. Baena, and figure 2 by Luiz A.W. Peixoto. The authors were funded by Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) (FCTL: grants # 2011/51532-7 and 2013/20936-0) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) (WBW: process # 304754/2011-0) Ver menos

Abstract: Hyphessobrycon montagi, new species, is described from tributaries of the Rio Arapiuns, a left margin affluent of the lower Rio Tapajós, Amazon basin, Pará, Brazil. The new species can be diagnosed from all its congeners by the possession of a combination of two well-defined humeral blotches, connected by a narrow stripe, and a caudal peduncle blotch. A putatively monophyletic Hyphessobrycon heterorhabdus species-group, restricted to H. heterorhabdus, H. amapaensis, and H. eschwartzae, is herein proposed based on shared derived features of color pattern. Alternative proposals of a "Hyphessobrycon heterorhabdus group" presented in the recent literature are evaluated and criticized Ver menos