Hypoptopoma is a genus of small armored catfish in the pleco family Loricariidae, placed in the subfamily Hypoptopomatinae alongside Otocinclus and its relatives. The atlas's species come from across the South American lowlands — Brazil, Peru, Bolivia, Colombia, Venezuela, Argentina, Ecuador, and Guyana. Like their otocinclus cousins, Hypoptopoma have flattened, elongated bodies plated in bony scutes, downturned sucker mouths for rasping algae and biofilm from wood and rock, and a low-slung profile suited to clinging in current. They run larger than most Otocinclus, though, with the atlas's size range reaching 5.5 in rather than the few centimeters typical of true otos. The atlas covers 13 species.
In the hobby, Hypoptopoma is sometimes marketed as a bigger, hardier alternative to Otocinclus for algae control, and species like Hypoptopoma elongatum and H. gulare — both sold as 'Giant Oto' — reflect that comparison directly, alongside the aptly named otocinclus-lookalike pleco (H. psilogaster). They are peaceful, herbivore-leaning grazers best suited to planted or driftwood-furnished tanks with established algae growth. Conservation-wise the genus is in good shape: every assessed species in the atlas carries a least concern rating, with no widespread threats currently recognized.