Otothyris is a genus of tiny armored catfish in the pleco family Loricariidae, part of the oto-type group of suckermouth catfish native to coastal river drainages of Brazil. The atlas's four species are all diminutive, with adults measuring only about 1–1.5 in — among the smallest loricariids covered on the site. Like their better-known relatives in Otocinclus, Otothyris fish have a flattened, armor-plated body and a ventral sucker mouth used to graze algae and biofilm off rocks, wood, and plant leaves in the flowing water they inhabit.
Otothyris species are seldom offered under their own name in the aquarium trade; small Brazilian oto-type catfish exported for the hobby are more often sold simply as 'Otocinclus' regardless of genus, so hard data on how often true Otothyris reach tanks is sparse. What is documented is a genus under real pressure: the atlas's IUCN tally includes a Critically Endangered rating alongside three Least Concern species, consistent with the tight, localized ranges typical of small Brazilian coastal-drainage fish that a single dam or pollution event can wipe out. Otothyris lophophanes (Brown Sucker Catfish) and O. travassosi (Fine Striped Oto) are the two species with recorded common names in the atlas.