Genus Trefusia de Man 1893 Type species Trefusia longicauda De Man, 1893 Diagnosis Amphideal fovea cryptospiral, oval, or horse-shoe shaped. Funnel-shaped buccal cavity. Males with ventral (and sometimes subventral) longitudinal rows of cervical sensillae. Small papillose pre-cloacal supplements present, situated either in a single ventral row or two sub-ventral rows; post-cloacal papillae absent. Spicules usually with handle-shaped proximal ends. Females with two ovaries. Tail conical, conico-cylindrical, or filiform. Remarks The last treatment of the genus Trefusia was by Keppner (1992), who provided an updated key to the males of the 17 species of the genus based on Riemann (1966). T. varians Gerlach, 1955 was not included in the key because the original description was based on female specimens only. Since then, Trefusia monodelphis Bussau, 1990 was synonymised with Trichistoma gracile Andrássy, 1985 by Andrássy (2007), and two new species were described by Bussau (1993). There are currently 20 valid Trefusia species (including T. piperata sp. nov.).

Published as part of Leduc, Daniel, 2013, Two new free-living nematode species (Trefusiina: Trefusiidae) from the Chatham Rise crest, Southwest Pacific Ocean, pp. 1-13 in European Journal of Taxonomy 55 on pages 2-3, DOI: 10.5852/ejt.2013.55, http://zenodo.org/record/3822945