Key to 28 genera of subfamily Hemiarthrinae Markham, 1972 (based on females)
1 Pleon without appendages.......................................................... Orophryxus Bruce, 1972a
- Pleon with appendages................................................................................. 2
2 Pleon without lateral plates............................................................................. 3
- Pleon with lateral plates................................................................................ 7
3 With sucker-like organ on the dorsum of the cephalon..................................... Neophryxus Bruce, 2007
- Without sucker-like organ on the dorsum of the cephalon...................................................... 4
4 Pereomere 1–6 with elongated, filiform coxal plates...................................... Filophryxus Bruce, 1972b
- Pereomeres without any coxal plates...................................................................... 5
5 With four pairs of biramous pleopods..................................................................... 6
- With four pairs of uniramous pleopods.............................................. Anomophryxus Shiino, 1937
6 With globose uropods............................................ Epiphrixus Nierstraz & Brender à Brandis, 1932
- Without uropods.................................................................. Hemiphryxus Bruce, 1978
7 With biramous lateral plates............................................................................. 8
- With uniramous lateral plates........................................................................... 11
8 With two pereopods on convex side of the body................................... Allodiplophryxus Markham, 1985
- With more than two pereopods on convex side of the body..................................................... 9
9 With seven pereopods on convex side of the body........................................ Cataphryxus Shiino, 1936
- With three or four pereopods on convex side of the body..................................................... 10
10 With three pereopods on convex side of the body.................................... Diplophryxus Richardson, 1904
- With four pereopods on convex side of the body..................................... Micropodiphryxus Boyko, 2012
11 Pereon with prominent coxal plates............................................... Izuohshimaphryxus Saito, 2015
- Pereon without coxal plates............................................................................ 12
12 With seven pereopods on convex side of the body........................................................... 13
- With fewer than seven pereopods on convex side of the body.................................................. 16
13 Pleon with four segments......................................... Apophrixus Nierstraz & Brender à Brandis, 1931
- Pleon with five segments.............................................................................. 14
14 With four pairs of biramous pleopods................................................... Eophrixus Caroli, 1930
- Without biramous pleopods............................................................................ 15
15 With four pairs of uniramous pleopods.............................................. Sigyn An, Boyko & Li, 2015
- With three pairs of uniramous pleopods.................................................... Loki Markham, 1972
16 With four pereopods on convex side of the body............................................................ 17
- With fewer than four pereopods on convex side of the body................................................... 19
17 With three pairs of uniramous pleopods, without uropods.................................. Mesophryxus Bruce, 1973
- With four pairs of uniramous pleopods, with uropods........................................................ 18
18. Pleon with five segments.......................................................... Eriphrixus Markham, 1990
- Pleon with four segments............................................................ Pliophrixus Caroli, 1930
19 With three pereopods on convex side of the body........................................................... 20
- With fewer than three pereopods on convex side of the body.................................................. 21
20 Second oostegite on long side arching over to dorsal surface............................ Mediophrixus Markham, 1990
- Second oostegite on long side not arching over to dorsal surface........................... Dicropleon Markham, 1972
21 With two pereopods on convex side of the body............................................................ 22
- With one pereopod on convex side of the body............................................................. 26
22 Pleon with five pleomeres............................................................................. 23
- Pleon with three pleomeres............................................................................ 25
23 With four pairs of uniramous pleopods................................................................... 24
- With four pairs of biramous pleopods............................. Hyperphrixus Nierstraz & Brender à Brandis, 1931
24 Attached dorsolaterally on host, pleomeres distinct dorsally............. Metaphrixus Nierstraz & Brender à Brandis, 1931
- Attached ventrally on host, pleomeres fused dorsally....................................... Anisarthrus Giard, 1907
25 With three pairs of uniramous pleopods, plus uropods.................................... Miophrixus Barnard, 1955
- With three pairs of biramous pleopods, without uropods................................ Anchiarthrus Markham, 1992
26 With three pairs of biramous pleopods, plus uropods............. Hypohyperphrixus Nierstraz & Brender à Brandis, 1932 - With four pairs of uniramous pleopods, without uropods..................................................... 27
27 Pleon of five segments, with lateral plates of same size........................... Hemiarthrus Giard & Bonnier, 1887
- Pleon of four segments, with lateral plates of first three pleomeres small, but very large on fourth..................................................................................................... Azygopleon Markham, 1985