Physopyxis is a genus of tiny banjo catfish in the family Aspredinidae, found across the freshwater drainages of the Amazon and Orinoco basins in Brazil, Venezuela, Colombia, Guyana and Peru. The atlas covers 3 species, and they are true miniatures even by banjo-catfish standards, ranging from about 1–2 in as adults. Like other aspredinids, the body shows the family's signature shape: a broad, flattened head and forebody that narrows sharply into a slender tail, giving the fish its banjo-like silhouette, with skin studded in small tubercles rather than the bony armour plates seen in many other catfish families.
These are bottom-dwelling fish of slow, often blackwater or leaf-litter-strewn stretches of river, where their cryptic shape and colouration help them blend into detritus and sediment. Physopyxis lyra, the lightning catfish, is the species most likely to be seen in specialist aquarium circles, prized for its bold zig-zag pattern, while Physopyxis ananas and Physopyxis cristata are little known outside ichthyological collections. None of the three carry a threatened IUCN status in the atlas record, and none are flagged under CARES. Where they are kept, tank setups mimic soft, slow-flowing water over a fine substrate with plenty of cover, since these are shy, small-mouthed fish rather than active community species.