Taxonomic key to male Trileptium (modified from NICHOLAS 2007)

1. Cuticle annulated, gubernaculum absent .............................. .................................................... T. iacobinum Wieser, 1959

1’. Cuticle smooth or annulated, gubernaculum present ........2

2. Buccal cavity with a single forwardly-directed dorsal onchium..................................................................................3

2’. Buccal cavity with dorsal and two sub-ventral onchia .......4

3. Supplement absent, gubernaculum without apophysis......... ...................................................... T. guttatum (Cobb, 1920)

3’. Supplement present, gubernaculum with a dorso-caudal apophysis ........................... T. subterraneum (Gerlach, 1952)

4. Supplement absent ................. T. salvadoriense Gerlach, 1955

4’. Supplement present .............................................................5

5. Dorsal onchium does not reach the mandibular transverse bar, sub-ventral onchia extend beyond bar........................6

5’. Dorsal and subventral onchia at same level, extend beyond mandibular bar ...................................................................7

6. Pre-cloacal supplement close to cloaca (6-11 µm) ................. ............................................ T. americanum (Keppner, 1987)

6’. Pre-cloacal supplement not close to cloaca (29 µm) ............. .............................................. T. otti Jensen & Gerlach, 1976

7. Spicules shallow arcs, gubernaculum does not loop over spicules ......................................................................................8

7’. Spicules strongly curved distally, gubernaculum with ventral peg, loops over both spicules...... T. australis Nicholas, 2007

8. Gubernaculum with dorso-caudal apophysis......................... ............................................................. T. ribeirensis sp. nov.

8’. Gubernaculum without apophysis .....................................9

9. Tail long and thin, 5 times body width at cloaca................... .................................................. T. longisetosum Inglis, 1966

9’. Tail 4 times or less than body width at cloaca ..................10

10. Gubernacula terminate in small plates each, with two lateral projections .................... T. parisetum Warwick & Platt, 1973

10’. Spicules cylindrical tapering to point, gubernaculum reduced to knob obscuring spicule tip ............................................... ........................................................ T. stylum Gerlach, 1956

10”. Gubernaculum without terminal projections; does not obscure spicule tip ............................... T. ayum Inglis, 1964