| Resumo: |
Lasiancistrus (Loricariidae: Hypostominae: Ancistrini) is diagnosed by the unique presence of a ventral strut of the pterotic and the presence of whiskerlike odontodes on the snout. Lasiancistrus has about 16 species assigned to it; however, only four are valid (L. schomburgkii, L. caucanus, L. guacharote, and L. heteracanthus), L. nationi is an Ancistrus, and L. trinitatus is incertae sedis in the Loricariidae. Lasiancistrus maracaiboensis and L. mystacinus are synonyms of L. guacharote; L. pictus, L. castelnaui, L. caquetae, L. guapore, L. multispinis, and L. scolymus are synonyms of L. schomburgkii; and L. planiceps, L. mayoloi, and L. volcanensis are synonyms of L. caucanus. Two new species are described: L. tentaculatus from the río Orinoco basin and L. saetiger from the rio Guama. The species can largely be told apart via color (L. schomburgkii has no or white spots on the fins, L. saetiger has entirely gray fins, and the rest have black spots in the fins), the presence of abdominal plates (L. caucanus, L. saetiger, and L. tentaculatus have naked abdomens, L. guacharote has a few small plates near the insertion of the pectoral fin, L. heteracanthus has a large patch of small plates, and L. schomburgkii is variable), and nuptial male condition (L. tentaculatus has small tentacles along the edge of the snout and the other species have a patch of whisker-like odontodes at the corners of the snout). Most species are widespread in piedmont regions of South America with L. schomburgkii occurring in the Amazon, Orinoco, and Essequibo basins.
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