Hypostomus johnii (Steindachner) was described from the rio Parnaíba basin in the state of Piauí and the rio São Francisco basin in the state of Bahia. Despite the good quality of the original description of H. johnii, it does not currently allow its distinction from congeners. Thus, H. johnii is redescribed based on the analysis of the types and several recently collected specimens. Recent collecting efforts of the rios Parnaíba and São Francisco basins resulted in specimens only being found in the rio Parnaíba basin. This raises doubts about whether H. johnii occurs in the rio São Francisco basin. The species is distinguished from its congeners by having a high number of teeth on the premaxilla and dentary (between 60-115); small to moderate-sized dark spots with a light background; absence of keels on flanks; and abdominal plates more evident on laterals. A lectotype of H. johnii is designated herein and H. eptingi is considered a junior synonym of H. johnii.
Ramos, T. P. A., Zawadzki, C. H., Ramos, R. T. da C., & Britski, H. A. (2017). Redescription of Hypostomus johnii, a senior synonym of hypostomus eptingi (Siluriformes: Loricariidae), Northeastern Brazil. Neotropical Ichthyology, 15(2). https://doi.org/10.1590/1982-0224-20160064