The phylogenetic position of the tardigrade species Grevenius annulatus was clarified using specimens from North-West Russia. Molecular phylogenetic analysis revealed close affinity of this species with the family Isohypsibiidae. At the same time, its isolated position within this clade, supported by a set of unique morphological and biological characters, prompted the distinguishing of a new genus Cucumibius gen. nov. A new genus Chilibius gen. nov. was also established for Isohypsibius sculptus. We provide a detailed description of the ultrastructure of C. annulatus comb. nov. body cuticle. The newly discovered presence of a complex cuticle of the ‘heterotardigrade type’ in the superfamily Isohypsibioidea is discussed. © 2024 Royal Swedish Academy of Sciences.