Xenurobrycon is a genus of exceptionally small characins, among the tiniest tetras in the Amazon basin - atlas species top out at only 0.5–1 in as adults, placing the genus alongside a handful of other miniaturized South American tetra lineages built around living in leaf litter and marginal vegetation rather than open water. In the atlas the genus is found across Brazil, Peru, Bolivia, and Ecuador, in the small forest streams and floodplain habitats typical of the region's dwarf characins. Xenurobrycon heterodon and Xenurobrycon polyancistrus both carry the local name mojarita, a diminutive fitting a fish barely larger than a fingernail.
A genus this small draws more interest from ichthyologists studying miniaturization in characins than from the general aquarium trade, though dedicated nano-fish keepers occasionally seek out true dwarf tetras of this kind for very small, densely planted setups. Because adult Xenurobrycon are so tiny, they are unsuited to typical community tanks and need calm tankmates and fine-particle foods sized to match their mouths. The conservation picture looks reasonably settled for the genus as assessed, with four of the six atlas species rated Least Concern and the remaining two Not Evaluated.