Phylogeny of Eutardigrada: new molecular data and their morphological support lead to identification of new evolutionary lineages

Seventy-nine specimens belonging to six of the nine current eutardigrade families have been considered in a wide and extensive study of the phylogeny of the largest class of Tardigrada (Eutardigrada). The molecular (18S rDNA) and morphological data partly support previous results. In particular, the applied integrative approach allowed us to find morphological synapomorphies, supporting the clusters here identified by molecular data and the previous taxa erected only on molecular basis. The class Eutardigrada has been confirmed and, within it, the orders Apochela and Parachela, the superfamilies Macrobiotoidea, Hypsibioidea and Isohypsibioidea, and all the families and subfamilies considered, even though in several cases with an emended diagnosis. In addition, new taxa have been erected: the superfamily Eohypsibioidea, the new families Hexapodibiidae and Isohypsibiidae, the new subfamily Pilatobiidae (Hypsibiidae) with the new genus Pilatobius, in addition to an upgrading to genus level of Diphascon and Adropion, to date considered subgenera of Diphascon. Our results demonstrate that while molecular analysis is an important tool for understanding phylogeny, an integrative approach using molecular and morphological data is necessary to fully elucidate evolutionary relationships.