The cladistic classification of Phthiracaroidea (Niedbała 1986) and Euphthiracaroidea (Mahunka 1990) (Acari, Oribatida), based on morphological symplesio- and synapomorphic characters has been subjected to verification by molecular analysis of mitochondrial COI and nuclear ITS2, 18S and 28S DNA regions. Twenty-one selected species from representative genera of both superfamilies were analyzed. The phylogenetic trees generated by maximum likelihood method confirm the classification of ptyctimous mites resulting from the analysis of morphological characters. Mesoplophoridae, representing the supercohorts Enarthronota, were placed separately to the clade Mixonomata containing Phthiracaroidea and Euphthiracaroidea that are in a sister relationship. The percentage of genetic divergence between the main clades is high in three markers (COI, ITS2 and 28S), it ranges from 36.8% to 38.7% in the barcode marker COI from 26.0% to 35.4% in ITS2 and from 16.2% to 30.0% in 28S, while in 18S it is very low (1.1% - 3.3%). In the Phthiracaroidea, two sister clades Steganacaridae and Phthiracaridae are distinguished. Steganacaridae include three clades Atropacarus, Hoplophthiracarus and Steganacarus with Steganacarus and Tropacarus as the sister clades. Closely related S. (T.) carinatus and S. (T.) pulcherrimus are separate species. Within the Euphthiracaroidea, the four clades: Mesotritia, Microtritia, Acrotritia and Euphthiracarus are resolved. Mesotritia is the most distant, and Microtritia and Acrotritia show the closest relationship.
