Exastilithoxus is a small genus of armored suckermouth catfish in the family Loricariidae, related to the rapids-dwelling Lithoxus group. The atlas's 2 species are native to Brazil and Venezuela, where they cling to rocks in fast, well-oxygenated rapids - a habitat that has shaped a flattened body, an enlarged sucker-disc mouth, and heavy bony armor plating that resists being swept downstream. They are small for plecos, running only about 2–2.5 in.
This is a specialist's genus rather than a mainstream aquarium fish: rapids-adapted Loricariidae of this kind need strong current and very well-oxygenated water, conditions most community tanks don't provide, so Exastilithoxus turns up only occasionally in the hobby, mostly among dedicated pleco keepers. The fringelip rapids pleco (Exastilithoxus fimbriatus) is the better-known of the two species. IUCN status is split between Data Deficient and Least Concern, reflecting how little survey work covers these remote, fast-water habitats.