Parotocinclus haroldoi is separated from most of its congeners by having an abdomen covered by relatively large plates (vs. naked abdomen or with small plates). This species occurs in Parnaíba River basin with two other congeners, P. cabessadecuia and P. cearensis. Parotocinclus haroldoi is distinguished from P. cabessadecuia for having developed adipose fin (vs. rudimentary or absent adipose fin) and P. cearensis, for having abdomen covered by entirely plates (vs. almost naked abdomen with small sparse plates). Parotocinclus haroldoi is known from the Parnaíba river basin in the state of Piauí, Maranhão-Piauí.
Corydoras difluviatilis é endêmica do Brasil e apresenta ampla distribuição, ocorrendo nos trechos superiores das bacias dos rios Paraná e São Francisco, onde é abundante e frequente. Por não apresentar ameaças significativas que coloquem em risco sua população, Corydoras difluviatilis foi categorizada como Menos Preocupante (LC).
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