Both sexes of a new genus and species, Lobopleura ambiducti (Copepoda, Harpacticoida), are described from a sandy beach on the Isle of Iona, Scotland. Within the family Ancorabolidae, the new genus is characterised by the following autapomorphies: paired genital system in both sexes; male P3 endopod-2 not secondarily subdivided; P4 endopod with only one apical seta and P5 baseoendopodal armature reduced to one vestigial seta. Lobopleura ambiducti is unique within the subfamily Laophontodinae in exhibiting the most plesiomorphic armature pattern on P1 endopod-2. Aspects of pre-copulatory mate guarding behaviour are discussed. Despite the absence of type material for direct comparison, Laophontodes expansus Sars, 1908, is transferred to Lobopleura based on the following combination of characters: dorsoventrally depressed body shape; somites with laterally produced lobate processes; wide bell-shaped cephalothorax; rostral shape and detailed morphology of antennule, antenna, mouthparts and first to fifth thoracopods. Material previously identified as Laophontodes sp. from County Dublin, Ireland, and Laophontodes expansus from Gullmarfjord, Sweden, proved upon re-examination to be conspecific with L. ambiducti, new genus, new species. An updated generic diagnosis is provided for Probosciphontodes Fiers, 1988, resulting from the re-examination of type material of Probosciphontes stellata Fiers, 1988, and P. ptenopostica Fiers, 1988. The presence of a minute antennary exopod bearing a single (reduced) seta is confirmed in all material of Lobopleura and Probosciphontodes examined. The strong support for a sistergroup relationship between Lobopleura and Probosciphontodes is discussed.