Arctodiphascon tenue (Thulin, 1928) Tumanov & Tsvetkova, 2023

Position of Arctodiphascon tenue , comb. nov. within Hypsibiidae

Our phylogenetic analyses revealed that despite the obvious morphological similarity with the genus Diphascon (presence of a drop-shaped dorsal apodeme between the rigid and the flexible part of the bucco-pharyngeal tube), the species A. tenue , comb.nov. clearly belongs to the phylogenetic clade currently designated as the subfamily Itaquasconinae ( Fig. 6). Within this clade, A. tenue forms a monophyletic clade with two Adropion -like species that have not been formally described ( Gąsiorek & Michalczyk, 2020). In our opinion, A. tenue should be excluded from the genus Diphascon due to its phylogenetic distance from this clade. However, taking into account its morphology, which is unique within the Itaquasconinae clade – the presence of the drop-shaped dorsal apodeme of bucco-pharyngeal tube – this species cannot be included in any of the currently existing genera of the Itaquasconinae . Therefore, we proposed the erection of a new genus Arctodiphascon gen. nov.