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

• The Eutardigrada phylogeny was performed on 129 specimens belonging to all families.
• The molecular phylogenies (18S and 28S rDNA) were compared with morphological data.
• New phylogenetic unexpected relationships and lineages were found.
• Pilatobiinae, Pilatobius new taxa, Adropion upgraded.
• Hypsibiidae, Calohypsibiidae, Itaquasconinae, Diphasconinae, Diphascon all emended.

An extensive study of the phylogeny of Eutardigrada, the largest class of Tardigrada, has been performed analyzing one hundred and forty sequences (eighty of which newly obtained) representative of one hundred and twenty-nine specimens belonging to all families (except Necopinatidae) of this class. The molecular (18S and 28S rRNA) results were compared with new and previous morphological data, allowing us to find new phylogenetic relationships, to identify new phylogenetic lineages, to erect new taxa for some lineages, and to find several morphological synapomorphies supporting the identified clusters. The class Eutardigrada has been confirmed and, within it, the orders Apochela and Parachela, the superfamilies Macrobiotoidea, Hypsibioidea, Isohypsibioidea, and Eohypsibioidea, and all the families and subfamilies considered, although with emended diagnoses in several cases. In addition, new taxa have been erected: the new subfamily Pilatobiinae (Hypsibiidae) with the new genus Pilatobius, as well as an upgrading of Diphascon and Adropion to genus level, previously considered subgenera of Diphascon. Our results demonstrate that while molecular analysis is an important tool for understanding phylogeny, an integrative and comparative approach using both molecular and morphological data is necessary to better elucidate evolutionary relationships.

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