Original description as Ptychochromis onilahy:
- Stiassny, Melanie & John S. Sparks. 2006. "Phylogeny and Taxonomic Revision of the Endemic Malagasy Genus Ptychochromis (Teleostei: Cichlidae), with the Description of Five New Species and a Diagnosis for Katria, New Genus". American Museum Novitates. (n. 3535); pp. 1–55 (crc01327) (abstract)
Conservation: Ptychochromis onilahy is evaluated by the international union for the conservation of nature in the iucn red list of threatened species as (EX) extinct (2016). Despite a number of collecting expeditions to southwestern Madagascar in recent years, no additional specimens referable to P. onilahy have been collected and the species may be extinct. However, many areas of southwestern Madagascar have not been thoroughly surveyed for freshwater fishes, and the Onilahy River basin is a large drainage system, thus, the possibility exists that remnant populations of Ptychochromis onilahy persist in more remote areas within the region (Stiassny et al., 2006).