A new species of Pseudancistrus from the Río Caroní, Venezuela (Siluriformes: Loricariidae)

Pseudancistrus reus is a new species from the Río Caroní (Río Orinoco drainage) of Venezuela known from two individuals. It differs from all other Pseudancistrus by having a color pattern consisting of alternating dark and light bars. In addition, it differs from all except P. genisetiger and P. papariae by having an incomplete mid-dorsal plate row and from P. genisetiger and P. papariae by having 18 contiguous mid-dorsal plates vs. 14 plates, a plateless break and then two more plates at the end of the caudal peduncle. The type locality of P. reus was submerged by the construction of the Caruachi dam, and is also the only known locality of the gymnotiform Sternarchorhynchus gnomus, making it imperative that the conservation status of these and other potential Caroní endemics be assessed. Pseudancistrus reus is the first species of Pseudancistrus sensu stricto from the Orinoco. Although the relationship of the species to other Pseudancistrus is unknown, P. reus may have gained access to the Orinoco either via stream capture between the Caroní and the Rio Uraricoera (Rio Branco – Rio Negro drainage) or via stream capture between the Caroní and either the Cuyuní or Mazaruni Rivers (Essequibo River drainage). key word: Siluriformes, Loricariidae, taxonomy