Identification key for World Halicoides species

1. Urosomite 1 smoth or with a dorsal bump, urosomite 2 with small or vestigial dorsal teeth........................... 2

- Urosomites 1–2 dorsally smooth or with dorsal bump, lacking teeth............................................. 3

2. Gnathopod 1, carpus and propodus with sparse setae; uropod 2, peduncle with row of robust setae; dorsal tooth of urosomite 2 small but distinguishable, reaching 1/6 of urosomite 3....................... Halicoides campensis sp. nov. (Figs. 3, 4)

- Gnathopod 1 ventral margin of carpus and propodus covered with setae; uropod 2, peduncle with 1 robust seta distally; dorsal tooth of urosomite 2 vestigial................................................ Halicoides tertia (Stephensen, 1931)

3. Pereopods 3–4, merus and carpus weakly robust.......................................................4 (Fig. 6)

- Pereopods 3–4, merus and carpus moderately to strongly robust..........................................6 (Fig. 3)

4. Upper lip rounded, not incised; pereopod 5, dactylus as long as propodus; uropod 3, outer ramus 2-articulated................................................................................. Halicoides iemanja sp. nov. (Figs. 5–7)

- Upper lip incised; pereopod 5, dactylus shorter than propodus; uropod 3, outer ramus 1-articulated..................... 5

5. Telson cleft to the base, 98% cleft............................................ Halicoides lolo (J.L. Barnard, 1971)

- Telson cleft almost to the base, 85% cleft.............................. Halicoides nana Birstein & Vinogradov, 1960

6. Uropod 3, outer ramus 1-articulated.............................................. Halicoides latilobata Ren, 2012

- Uropod 3, outer ramus 2-articulated........................................................................7

7. Antenna 1, article 2 of peduncle with oval structure.......................................................... 8

- Antenna 1, article 2 of peduncle lacking oval structure....................................................... 9

8. Gnathopod 1, dactylus slightly convex; epimeral plate 3, posterodistal angle with a marked tooth; uropod 1, ramus subequal to peduncle; uropod 3, article 2 of outer ramus short but distinguished.................. Halicoides anomalus Walker, 1896

- Gnathopod 1, dactylus strongly convex; epimeral plate 3, posterodistal angle with a tiny denticle; uropod 1, peduncle longer than ramus; uropod 3, article 2 of outer ramus vestigial..................... Halicoides borealis Johansen & Vader, 2018

9. Gnathopod 1, carpus and propodus long and very thin, subequal in length; coxae 3–4 longer than large, almost reaching half the length of basis................................................... Halicoides indica Birstein & Vinogradov, 1964

- Gnathopod 1, carpus shorter than propodus; coxae 3–4 short, larger than long, reaching at most 1/4 the length of basis.... 10

10. Palp of mandibles, article 3 as long as article 2............................ Halicoides anacantha (K.H. Barnard, 1925)

- Palp of mandibles, article 3 at most 50% of length of article 2................................................. 11

11. Coxa 1 acutely produced.............................................................................. 12

- Coxa 1 not produced, with rounded edges................................................................. 13

12. Upper lip incised; pereopod 5, dactylus shorter than propodus....................... Halicoides walkeri (Ledoyer, 1973)

- Upper lip rounded, not incised; pereopod 5, dactylus as long as the propodus......... Halicoides discoveryi Thurston, 1976

13. Pereopod 6, basis without poterodistal lobe; epimeral plate 3 with straight posterior margin and quadrate posteroventral corner.............................................................. Halicoides synopiae (J.L. Barnard, 1962)

- Pereopod 6, basis with poterodistal lobe reaching the end of ischium; epimeral plates 1–3 with a distinct small tooth at the posteroventral corners................................................. Halicoides tambiella (J.L. Barnard, 1961)