Vaillantella is a small genus of loaches placed in its own family, distinct from the familiar Botiidae and Cobitidae loach groups, restricted to fast-flowing forest streams of Sundaland - Indonesia, Malaysia, and Brunei. Atlas species range 2–4 in. The genus is best recognised by its long, slender body and a deeply forked, scissor-like tail fin, unusual among loaches and reflected directly in the common name of the brown fork-tail loach, V. cinnamomea.
This is a genus of scientific rather than aquarium interest - it rarely, if ever, appears in the ornamental fish trade, and what is known comes mostly from field surveys of Borneo and Sumatra's hill streams rather than hobbyist experience. Conservation status reflects that same gap: three of the four atlas species are Not Evaluated and the fourth is Data Deficient, meaning none has been formally assessed against extinction-risk criteria - a common situation for narrow-range stream fish in a region where survey effort has lagged well behind habitat loss from logging and land conversion.