The terrestrial nematode genus Teratocephalus de Man, 1876, includes at present 29 bacteria feeding species. They occur particularly on mosses and sometimes in semi-aquatic habitats world-wide (including Antarctica). Their morphology makes them easy to recognize: all are relatively small with a strongly annulated cuticle. Males are rare. Although they do not have any phasmids nor a bursa, they were often placed within the Rhabditida (=”Secernentia” or “Phasmidia”). At present they are positioned in clade 7 of the basal Chromadoria (see also van Megen et al., 2009).