Eonemachilus is a small genus of stone loaches in the family Nemacheilidae, the slender, bottom-hugging loaches that dominate the fast-flowing streams of continental Asia. The atlas covers 2 species, both known only from China, matching the elongate, near-cylindrical body plan, reduced or absent scales, and small ventral mouth typical of the family - built for gripping rocky substrate in current rather than for open swimming. At roughly 3 in, they sit in the ordinary size range for a nemacheilid.
These are obscure, taxonomically described species rather than aquarium fish, and data on their biology is sparse outside the scientific literature. One of the two species carries an IUCN status of Endangered, which for a small-range Chinese stream loach usually points to a narrow catchment vulnerable to damming, pollution, or other habitat disturbance rather than any direct collection pressure - the genus is essentially unknown in the hobby.