Two new marine species of Gastrotricha: Chaetonotidae are described from West Greenland and Denmark. Some peculiar features suggest the affiliation of the two species to a new genus, for which the name Diuronotus is proposed. The affinity of these gastrotrichs with species of Musellifer, the only genus entirely marine and hermaphroditic, and possibly the most basal one along the Chaetonotidae evolutionary line, is discussed from a morphological point of view. The span of the geographical distribution of Diuronotus is discussed in the light of a record of an additional co-generic, undescribed species from the USA. The relationships of this genus will be important in reconstructing the evolutionary pathways within Gastrotricha: Chaetonotida.