Previous taphonomic studies about the calmoniid trilobites of the Ponta Grossa Formation, Apucarana sub basin, revealed that some species might correspond to artificial taxa, or taphotaxa, whose diagnostic characters are artifacts of the fossilization process. This article presents a systematic revision of the Calmoniidae, and a discussion about the influence of taphonomy in the preservation of the diagnostic characters of this group, which can be altered by the external factors that they are exposed to. The most current record comprised 17 species of calmoniids in the Ponta Grossa Formation; an inaccurate number because it included invalid species that were never duly published, as well as some taphotaxa. At least eight species of calmoniids can be considered as artificial: Calmonia? gonzagana Clarke, C. signifer var. micrischia Clarke, Metacryphaeus granulata Popp, M sedori Popp, Tibagya parana Struve, Paracalmonia pessula Clarke, P. salamunii Popp et al., and P mendesi Popp et al., and are herein synonymized with previously erected species. This revision highlights the importance of allying a taphonomic vision with the taxonomic studies in order to reach a more accurate depiction of the calmoniid diversity. Furthermore, the designation of new species should be based preferably on numerous, well-preserved specimens in order to avoid the erection of artificial taxa.
