Corydoras similis was described by Hieronimus in1991. Before its description this catfish was already available in the trade and it became known as Corydoras spec. described "violet". As only Hieronimus this Corydoras in the magazine for fish news (Jg.1; No.1 described) it got the name Corydoras similis. Hieronimus states the holotype location as being from Brazil, from an influx to the Rio Madeira near the city of Ariqumes. Hieronimus also states that Corydoras similis and Corydoras ourastigma are from the same area, the Rio Branco catchment area in the Brazilian federal state Roraima. The federal state Rondonia reaches to the border with Bolivia and the federal state Roraima borders on Venezuela and Guyana, approx. 900 km between the two locations! Since the location of the Holotype is decisive, this second location detail is doubtful.