Original description as Xiphophorus pygmaeus:
- Hubbs, Carl Leavitt & M. Gordon. 1943. "Studies of cyprinodont fishes. XIX. Xiphophorus pygmaeus, new species from Mexico". Copeia. 1943(1):31-33 (ffm00064)
Conservation: Xiphophorus pygmaeus is evaluated by the international union for the conservation of nature in the iucn red list of threatened species as (DD) data deficient (2018). Although the Huichihuayan and Axtla rivers carry enough flow and most areas remain in very good shape, with some remaining pristine areas, deforestation, pesticides, fertilizers and pollution (particularly around Huichihuayan) are common problems that affect them and have to be resolved, particularly in view of human population increase in the area.