Species of the Macrobiotus hufelandi group are one of the most often recorded tardigrades throughout the globe. For over a century M. hufelandi has been considered cosmopolitan but in recent decades numerous species of similar morphologies have been described from various continents, which suggests that what was originally defined as a single taxon is, in fact, a complex of species. The definition of the hufelandi group is subject to a long-standing discussion and in this paper we propose a refined set of characters that are hoped to elucidate the taxonomic status of the group. In order to aid interspecific comparisons, we also propose a unified nomenclature for the crucial morphological traits and clar.
Keywords: Tardigrada, chorion, egg shell, diagnostic key, Eutardigrada, Macrobiotidae, morphology, morphometry, nomenclature, Parachela, systematics, taxonomy.