Pseudotocinclus is a genus of small armored catfish in family Loricariidae, subfamily Hypoptopomatinae - the same broad group as the popular Otocinclus algae-eaters, though a distinct genus. It is endemic to short coastal river drainages of southeastern Brazil, including the Tiete and Paraiba do Sul systems. The atlas's three species are diminutive fish, only 1.5–2.5 in, sharing the flattened, bony-plated body and sucker-mouth typical of the subfamily, built for grazing algae and biofilm off rocks and wood in flowing water.
Pseudotocinclus is barely known in the aquarium hobby and is best understood as a conservation case rather than a trade species. Its coastal Brazilian range overlaps some of the country's most heavily urbanized and industrialized watersheds - the Tiete, in particular, has suffered severe pollution as it passes through greater Sao Paulo - and the genus's IUCN tally reflects that pressure starkly: one species Critically Endangered, one Endangered, and one Near Threatened. All three named species, including the Tiete Cascudinho, P. tietensis, are found only in Brazil.