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Outdated and inaccurate original descriptions of species nominal for genera or species complexes give birth to notorious difficulties in species identification and often translate into erroneous classifications of multiple species as one. This, in turn, results in severe overestimations of specific geographic ranges and ultimately in underestimations of the diversity of organisms living on our planet. Tardigrades, ubiquitous microscopic metazoans exhibiting relatively few taxonomically useful traits, bear many such problematic species. In this paper, we investigated, morphologically and molecularly, 10 European populations of Ramazzottius cf. oberhaeuseri (Doyère, 1840), a putatively cosmopolitan nominal species for the family Ramazzottiidae. The analysis of COI sequences revealed eight potential species, including one from Paris, the type locality of R. oberhaeuseri, which we used to integratively redescribe the nominal taxon. The identification of seven further species in a handful of samples collected from a single continent explicitly shows the considerable undescribed species diversity within this group and puts in question the cosmopolitan distribution of R. oberhaeuseri. The integrative redescription of R. oberhaeuseri opens the opportunity for descriptions of other species in the complex.http://zoobank.org/urn:lsid:zoobank.org:pub:50B99B53-C317-4DBD-8CF1-16297B85C4F3
Stec et al. (Tue,) studied this question.