A new species of Ancistrus (Siluriformes: Loricariidae), with a redescription of Ancistrus brevipinnis and further evidence of hidden diversity in the laguna dos Patos system, Brazil

A new species of Ancistrus is described from the rio Vacacai drainage, rio Jacui basin, laguna dos Patos system, southern Brazil. The new species differs from A. brevipinnis, the common species in the laguna dos Patos system, by having a dark brown to black background body color and dorsal and caudal fins plain dark, without lighter spots or bands. A morphometric and molecular comparison of different populations of A. brevipinnis from the laguna dos Patos system suggests that previously undetected species diversity is present in that basin. The typelocality of A. brevipinnis, originally described as Rio Grande do Sul State, is herein restricted to the rio Camaqua sub -basin of the laguna dos Patos system, and a redescription of A. brevipinnis is provided based on that population.