Description of three known and two new species of the genus Tylocephalus Crossman, 1933 with a revised taxonomy of the genus and key to species of the subfamily Wilsonematinae (Plectida)

Descriptions of populations of Tylocephalus auriculatus, T cephalatus, T nimius, T longicornis sp. n. and T primitivus sp. n. are given on the basis of studies with light and scanning electron microscopy. T longicornis sp. n. is characterised by a body length of 540-560 mum cervical cuticular expansions bearing 20-25 annules and extending well posterior to the level of "subcephalic" setae, cornua 13 mum long with filiform terminus, tail 43-45 mum long, 49-57 somatic and 7 caudal setae. T primitivus sp. n. is characterised by a body length of 300-450 mum, weakly developed cervical Cuticular expansions bearing 7-11 annules and extending halfway to the level of "subcephalic" setae, cornua cylindrical and 35 mum long, tail 28-46 mum long, 10-16 somatic and 3-5 caudal setae. An emended diagnosis and a revised classification of the genus Tylocephalus, and a key for identification of species in the subfamily Wilsonematinae are given.