Reaching the Monophyly: Re-Evaluation of the Enigmatic Species Tenuibiotus hyperonyx (Maucci, 1983) and the Genus Tenuibiotus (Eutardigrada)

SIMPLE SUMMARY: The tardigrade species Tenuibiotus hyperonyx (Maucci, 1982) was described forty years ago from the highest mountain of the Sella Group within the Dolomites (Italy), and so far, it is known only from its type locality. Due to the morphological characters of the claws, it has been included in the genus Tenuibiotus (Pilato & Lisi, 2011). By conducting the integrative and phylogenetic analyses, we pinpointed the phylogenetic position of the species, which turned out to be positioned within the genus Diaforobiotus Guidetti et al., 2016. As the phenotypic characters of the examined species fit the diagnosis of this genus, we proposed a new combination, Diaforobiotus hyperonyx (Maucci, 1982) comb. nov. Furthermore, we looked more closely for the morphological diversity noted within the genus Tenuibiotus, clarifying phenotypic uncertainties regarding Tenuibiotus willardi (Pilato, 1977) and Tenuibiotus bozhkae Pilato, Kiosya, Lisi, Inshina & Biserov, 2011. This action leads to uniformization of the genus diagnosis from the morphological point of view, which brings it closer to being considered as monophyletic. ABSTRACT: Revisions and redescriptions of taxa described in the past and that are now categorized as insufficiently diagnosed often play a crucial role in making further progress in modern taxonomy in many groups of organisms. Here we revised an enigmatic tardigrade species Tenuibiotus hyperonyx (Maucci, 1983) based on the newly discovered topotypic population from the Italian Alps. We performed an integrative analysis of morphological and genetic data in order to present an upgraded species description and elucidate its phylogenetic position. Our results enabled us to confidently place T. hyperonyx within the family Richtersiusidae, as a member of the genus Diaforobiotus. This change, together with a re-assessment of microphotographs of the Tenuibiotus willardi (Pilato, 1977) and Tenuibiotus bozhkae Pilato, Kiosya, Lisi, Inshina & Biserov, 2011 types, led to the discussion on species composition with narrative taxa amendments for the taxonomic parties involved in the proposed alteration.