Systematicians usually struggle with numerous undescribed and new species of poorly know organisms during biodiversity surveys and taxonomic studies.
In this recently published PLoS One contribution however, Indian, Czech and Slovak colleagues together with the team of J. Mariaux reached a rather unusual result: Their goal was to assess the diversity of a group of parasitic flatworms infesting freshwater fishes in the Indomalayan region. Their comprehensive study included multiple collecting field trips, as well as a complete morphological, molecular and ultrastructural revision of these worms. Surprisingly it demonstrated that only 4 species were present although… 47 had been previously described! This kind of revision allowed to untangle an extreme case of systematic confusion that was created by erroneous interpretations of the morphological variation in these worms. It also offers practical tools to unambiguously differentiate the existing taxa in this group.