Pseudohemiodon is a genus of whiptail catfish in the pleco family, distributed across a broad swath of South America, from the Amazon and Orinoco basins south into the Paraná-Paraguay-Uruguay system. Like other Loricariinae whiptails, its species have a strongly elongated, flattened body and tail that let them lie motionless on sand or leaf litter, camouflaged against predators, using an armoured sucker-mouth to graze algae and biofilm. Atlas sizes range from a modest 3.5 in up to a substantial 11.5 in for the largest species.
The genus is best known in the hobby for an unusual reproductive strategy shared with several whiptail relatives: males carry the fertilized egg mass attached to the underside of the body, between the pelvic fins, sheltering the eggs there until they hatch rather than guarding them in a cave. The chameleon whiptail (Pseudohemiodon apithanos) adds a further curiosity, an ability to shift body tone to match the surrounding substrate. Most Pseudohemiodon suit patient keepers running sand-and-driftwood biotope tanks rather than mainstream aquarium setups; the genus's conservation picture leans Least Concern, with two atlas species Data Deficient.