Some have drops and some do not, but can we rely on that? Re-investigation of Diphascon tenue (Tardigrada: Eutardigrada) with discussion of the phylogeny and taxonomy of the superfamily Hypsibioidea

An integrative description of a newly discovered Spitsbergen population of Diphascon tenue Thulin, 1928 was undertaken using high quality light microscopy, scanning electron microscopy and methods of molecular taxonomy. Phylogenetic analyses indicated the relationships of this species within the subfamily Itaquasconinae Bartoš in Rudescu, 1964 (the family Hypsibiidae Pilato, 1969). Arctodiphascon gen. nov. is erected with two species, A. tenue, comb. nov. and A. wuyingensis (Sun et al., 2020), comb. nov. Following the results of the phylogenetic molecular and morphological analysis, Adropion greveni (Dastych, 1984) and A. mauccii (Dastych et McInnes, 1996) are transferred to the genus Diphascon Plate, 1888 as D. greveni Dastych, 1984, stat. resurr. and D. mauccii Dastych et McInnes, 1996, stat. resurr. Following the results of the phylogenetic molecular and morphological analyses, the generic name Meplitumen Lisi et al., 2019, syn. nov. is recognised as synonymous to Platicrista Pilato, 1987. An emended diagnosis for the genus Astatumen Pilato, 1997 is given. The distribution of morphological characters within the superfamily Hypsibioidea is analysed and their taxonomic significance is discussed. A new phylogenetic tree of Hypsibioidea based on molecular data is presented. The subfamilies Itaquasconinae and Pilatobiinae Bertolani et al., 2014 are raised to family rank, as Itaquasconidae and Pilatobiidae (status promotus). The subfamily Diphasconinae Dastych, 1992 is transferred to the Hypsibiidae, as a sister group to the subfamily Hypsibiinae Pilato, 1969.