A. unicolor was originally described as Plecostomus unicolor by Franz Steindachner in 1908. It was subsequently listed as a member of Aphanotorulus by I. J. H. Isbrücker, I. Seidel, J. Michels, E. Schraml, and A. Werner in 2001.[4] In 2004, Jonathan W. Armbruster classified the species within Hypostomus instead of Aphanotorulus.[5] In 2016, following a review of Isorineloricaria and Aphanotorulus by C. Keith Ray and Armbruster (both of Auburn University), the species was transferred once again to Aphanotorulus.[5]
