Keponinae, Boyko, Moss, Williams & Shields, 2013

An, Jianmei, Zheng, Wanrui, Liang, Jielong & Paulay, Gustav, 2020, Three new species of Scyracepon Tattersall, 1905 (Isopoda: Bopyridae) from Pacific islands, with comments on the rarity of bopyrids parasitizing brachyurans, Zootaxa 4851 (1), pp. 151-162 : 160-161

Key to 29 genera of the subfamily Keponinae (Hemicepon and Metathelges based on immature type specimens are excluded)

1 Abdominal parasites, female with almost smooth lateral plates and pleopods ............................... Rhopalione

- Branchial parasites, female usually with digitate or tuberculate lateral plates and pleopods......................... ... 2

2 All pereomeres of female normally developed ............................................................... 3

- Pereomere 2 of female almost absent ............................................................ Onychocepon

3 One pair of lateral plates on every pleomere of female ......................................................... 4

- Two pairs of lateral plates on every pleomere of female ............................................. .. Cardiocepon

4 Female with some middorsal projections .................................................................... 5

- Female without middorsal projections .................................................................... 13

5 Endopodite of pleopod of female well-developed.......................................................... ... 6

- Endopodite of pleopod of female reduced or absent .......................................................... 10

6 All male pleomere segments distinct ....................................................................... 7

- Some male pleomere segments fused .............................................................. Scyracepon

7 Female with middorsal projection on pleomere 1 ..................................................... Megacepon

- Female without middorsal projection on pleomeres ........................................................... 8

8 Antennae of female as long as body ................................................................... Ergyne

- Antennae of female much shorter than body .......................................................... Allokepon

9 Pleopods of female without endopodites ............................................................ Mesocepon

- Pleopods of female with reduced endopodites ............................................................... 10

10 Middorsal projections only on last 2 pereomeres of female ..................................................... 12

- Middorsal projections on more than last 2 pereomeres of female ................................................ 11

11 Lateral plates and pleopods of female with digitate margins ........................................... Cancricepon

- Lateral plates and pleopods of female with smooth margins........................................... .. Paracepon 12 Pereomere 6 of female with more than one projection .................................................. Tylokepon

- Pereomere 6 of female with one projection ......................................................... Grapsicepon

13 Pleopods of female with well-developed endopodites ......................................................... 14

- Pleopods of female with reduced endopodites .............................................................. 22

14 Tergal projection of female with densely tuberculate surface ............................................ Lobocepon

- Tergal projection of female with almost smooth surface ....................................................... 15

15 Lateral plates and pleopods of female with smooth margins ................................................... 16

- Lateral plates and pleopods of female with digitate margins................................................. ... 18

16 Male with lateral plates........................................................................ .. Procepon

- Male without lateral plates .............................................................................. 17

17 Female with wide lamellar lateral plates, male with slender uropods.................................... .. Coxalione

- Female with narrow striped lateral plates, male with stout uropods.................................... ... Hypocepon

18 Head of female with bilobate anterior margin ............................................................... 19

- Head of female with convex anterior margin ............................................................... 21

19 Lateral plates and pleopods of female covered with tubercles, margins sparsely digitate ....................... Anacepon

- Lateral plates and pleopods of female smooth, margins densely digitate .......................................... 20

20 Female with endopodites of pleopods slightly shorter than exopodites, barbula with 2 pairs of projections ............ Kepon

- Female with endopodites of pleopods much shorter than exopodites, barbula with 3 pairs of projections ....... Dactylocepon

21 Male without pleopods ......................................................................... Metacepon

- Male with pleopods ........................................................................... Heterocepon

22 Female with 5 pairs of biramous pleopods plus uropods ................................................ Castrione

- Female with 5 pairs of uniramous pleopods plus uropods ..................................................... 23

23 Lateral plates of female with largely smooth margins ......................................................... 24

- Lateral plates of female with digitate margins ............................................................... 25

24 Exopodites of pleopods of female slightly shorter than corresponding lateral plates .......................... .. Epicepon

- Exopodites of pleopods of female much shorter than corresponding lateral plates ......................... .. Atypocepon

25 Male with all pleomeres fused ................................................................... Hypercepon

- Male with some pleomeres separated ...................................................................... 26

26 Female with reduced frontal lamina ................................................................ Apocepon

- Female with well-developed frontal lamina ................................................................ 27

27 Frontal lamina of female tuberculate ............................................................... Onkokepon

- Frontal lamina of female smooth ......................................................................... 28

28 Male with long uropods.......................................................................... .. Leidya

- Male with short uropods ...................................................................... Trapezicepon