Paraloricaria is a genus of whiptail catfish in family Loricariidae, subfamily Loricariinae, native to the southern Rio de la Plata drainage of South America - the Parana, Paraguay, and Uruguay river systems shared by Argentina, Uruguay, Brazil, and Paraguay. The three atlas species - P. agastor, P. commersonoides, and the Viola catfish (P. vetula) - show the elongated, flattened, camouflage-patterned body and long tapering caudal fin typical of whiptail loricariids, an adaptation for lying motionless among sand, leaf litter, and driftwood while grazing algae and biofilm with a ventral sucker-mouth. Adult size varies widely across the genus, from around 4.5 in up to over 19.5 in.
The Viola catfish is the species most likely to be seen in the hobby, valued by loricariid specialists for its slender, patterned shape and relatively subdued, sand-sifting temperament; because whiptails of this genus come from cooler, more temperate rivers than typical Amazonian plecos, they generally do best at moderate rather than tropical temperatures and appreciate a fine sand substrate to forage in. Most of the genus is assessed as Least Concern by the IUCN, consistent with fish distributed across a large, still relatively intact river system, though one species remains unevaluated.