Systematics and biogeography of the genus Phalloceros Eigenmann, 1907 (Cyprinodontiformes: Poeciliidae: Poeciliinae), with the description of twenty-one new species

The genus Phalloceros is revised. Phalloceros caudimaculatus (Hensel, 1868) and twenty-one new species are recognized in Phalloceros. The species and their distributions are: P. alessandrae, small coastal drainages of the Parana State; P. anisophallos, small coastal drainages of the Rio de Janeiro State; P. aspilos, rio Parati-Mirim, Rio de Janeiro; P. buckupi, small coastal drainages of the Parana State; P. caudimaculatus (Hensel, 1868), laguna dos Patos system, lower rio Uruguay, drainages of rio Tramandai, rio Mampituba and coastal drainages of Uruguay and Argentina; P. elachistos, rio Doce drainage and small coastal drainages of the Espirito Santo State; P. enneaktinos, corrego da Toca do Boi, Rio de Janeiro; P. harpagos, rio Parana-Paraguai basin and coastal drainages from Espirito Santo to Santa Catarina States; P. heptaktinos, rio Jacui drainage; P. leptokeras, middle portions of rio Paraiba do Sul drainage; P. leticiae, upper rio Araguaia; P. lucenorum, rio Juquia drainage; P. malabarbai, coastal drainage of the Santa Catarina State; P. megapolos, drainages of rio Sao Joao, rio Cubatao (North) and small adjacent drainages of the Parana State; P. mikrommatos, rio Joao de Tiba basin, a coastal drainage of the Bahia State; P. ocellatus, coastal drainages of the Bahia and Espirito Santo States; P. pellos, small coastal drainages of the Parana State; P. reisi, headwaters of rio Tiete, rio Paraiba do Sul, rio Ribeira de Iguape, and small coastal drainages of the Sao Paulo State; P. spiloura, coastal drainages of the Rio Grande do Sul and Santa Catarina States; P. titthos, coastal drainages of the Parana State; P. tupinamba, rio Itamambuca and rio Macacu drainages, small coastal drainages of the Sao Paulo and Rio de Janeiro States, and P. uai, rio Sao Francisco basin. A lectotype for Girardinus caudimaculatus is designated. Diagnoses of intrageneric clades of Phalloceros are provided. Diagnoses and descriptions of distributions are provided for each species as well as a key for identification. Phylogenetic and biogeographical features of Phalloceros are discussed.