What is a ‘strong’ synapomorphy? Redescriptions of Murray’s type species and descriptions of new taxa challenge the systematics of Hypsibiidae (Eutardigrada: Parachela)
Piotr Gąsiorek, Brian Blagden, Witold Morek, Łukasz Michalczyk
Abstract
Abstract Hypsibiidae are the most species-rich group within the Hypsibioidea, and three (Diphasconinae, Itaquasconinae, and Pilatobiinae) of its four subfamilies are characterized by a division of the foregut into a rigid buccal and a flexible pharyngeal tube. The aim of this work is to provide a comprehensive background for sound taxonomic studies on several hypsibiid lineages. We redescribe the type species for the genera Adropion, Guidettion, and Platicrista, and provide diagnostic keys for several genera. We also demonstrate that the presence of an apodeme at the border of the buccal and pharyngeal tube is not a discriminative criterion separating Diphasconinae from Itaquasconinae and that the apodeme does not have a uniform morphology among Hypsibiidae. Itaquascon serratulumsp. nov. (Uganda) is the first integratively described species in the genus. Furthermore, new species of Platicrista are described: Platicrista borneensissp. nov. (Malaysia), Platicrista carpathicasp. nov. (Poland), and Platicrista niveasp. nov. (Taiwan). Moreover, Raribius minutissimussp. nov. (Scotland) is described from leaf litter. Finally, Pilatobius is divided into four morphogroups by cuticular sculpturing and dorsal gibbosities, which serve as decisive criteria; two received phylogenetic support and are erected as Degmiongen. nov. (the oculatus group) and Fontouriongen. nov. (the recamieri group).