Key to the genera of suborder Trefusiina ( Simpliconema not included due to lack of data on females, but see Fig. 9 for pictorial key of all genera)

1. Female reproductive system monodelphic ....................................................................................... 2 – Female reproductive system didelphic ........................................................................................... 10

2. Female reproductive system monodelphic with anterior ovary ........................................................ 3 – Female reproductive system monodelphic with posterior ovary ...................................................... 8

3. Cephalic capsule present ................................................................................... Xennella Cobb, 1920 – Cephalic capsule absent .................................................................................................................... 4

4. Buccal cavity with teeth .................................................................................................................... 5 – Buccal cavity without teeth .............................................................................................................. 6

5. Cephalic setae and outer labial setae in single circle .................................... Tripylina Brzeski, 1963 – Cephalic setae and outer labial setae in separate circles ............................ Trischistoma Cobb, 1913

6. Female gonad and intestine both ending in cloaca ........................................................................... 7 – Vulva located very close to anus .......................................... Lauratonematoides De Coninck, 1965

7. Asymmetric male copulatory apparatus, gubernacular apophyses present ........................................ ....................................................................................................... Lauratonemella Tchesunov, 1984

– Symmetric male copulatory apparatus, gubernacular apophyses absent ............................................ ............................................................................................................... Lauratonema Gerlach, 1953

8. Buccal cavity small, funnel-shaped ........................................................... Rhabdocoma Cobb, 1920 – Buccal cavity large, with cuticularized walls ................................................................................... 9

9. Buccal cavity uncompartmentalized, amphid elongate ...... Africanema Vincx & Furstenberg, 1988 – Buccal cavity with discontinuity between gymnostoma and stegostoma, amphid pocket-shaped with oval or circular opening ............................................................................ Halanonchus Cobb, 1920

10. Pairs of discoid supplements present in pre- and post-cloacal regions of male ................................. .................................................................................................................... Cytolaimium Cobb, 1920 – Discoid supplements absent .............................................................................................................11

11. Cephalic setae and outer labial setae in single circle ........................ Trefusialaimus Riemann, 1974 – Cephalic setae and outer labial setae in separate circles ................................................................. 12

12. Female reproductive system with two posterior ovaries, outer labial setae not jointed, secretoryexcretory pore on setiform elevation .............................................................. Porocoma Cobb, 1920

– Female reproductive system with two opposed and reflexed ovaries, jointed outer labial setae, secretory-excretory pore not on setiform elevation ....................................... Trefusia De Man, 1893