Cerapus (Male), 1817

Nurshazwan, J., Ahmad-Zaki, A. B. & Azman, B. A. R., 2020, A new species of Cerapus (Amphipoda: Senticaudata: Ischyroceridae) from Pulau Bum Bum, Sabah, Malaysia, with an identification key to Cerapus species, Zootaxa 4802 (3), pp. 519-533 : 531

Key to the species of Cerapus (Male)

1. Uropod 1 with conspicuously large lateral peduncular hook on ventrodistal margin................................. 2 - Uropod 1 without hook on ventrodistal margin.............................................................. 5 2. Pereonites 1–2 with constriction......................................................................... 3 - Pereonites 1–2 without constriction....................................................................... 4 3. Gnathopod 2 propodus 3.5 times as long as wide..................................................... C. cudjoe - Gnathopod 2 propodus twice as long as wide........................................................ C. slayeri 4. Gnathopod 2 propodus 3 times as long as wide................................................... C. ryanadamsi - Gnathopod 2 propodus twice as long as wide....................................................... C. thomasi 5. Telson entirely cleft................................................................................... 6 - Telson semi-cleft or partially cleft........................................................................ 9 6. Rostrum conspicuously short............................................................................ 7 - Rostrum well developed................................................................................ 8 7. Pereopod 7 basis with spines along posteroproximal margin............................................ C. tubularis - Pereopod 7 basis without spines along posteroproximal margin............................................ C. erae 8. Pereonites 1–2 with constriction............................................................. C. micronesicus - Pereonites 1–2 without constriction.............................................................. C. oceanicus 9. Telson with deep cleft (> 50%)......................................................................... 10 - Telson with shallow cleft (<45%)....................................................................... 12 10. Telson with recurved spines on two transverse rows......................................................... 11 - Telson with recurved spines on three transverse rows................................................... C. nudus 11. Telsonic lobe with eight recurved spines on two transverse rows...................................... C. longirostris - Telsonic lobe with three recurved spines on two transverse rows............................ C. bumbumiensis sp. nov. 12. Telson with two transverse rows of spines................................................................. 13 - Telson with 6–7 longitudinal rows of spines.......................................................... C. orteai 13. Telson with a number of anteriorly-directed spines in two transverse rows....................................... 14 - Telson with six or seven posteriorly-directed spines in two transverse rows.............................. C. calamicola 14. Pereopod 6 coxa with long or short setae on ventral margin................................................... 15 - Pereopod 6 coxa without setae on ventral margin........................................................... 16 15. Pereopod 5 merus with more than one plumose seta on posterior lobe.................................... C. pacificus - Pereopod 5 merus with one plumose seta on posterior lobe............................................ C. chaomai 16. Rostrum short, less than 20% of head length............................................................... 17 - Rostrum long, more than 20% of head length.............................................................. 19 17. Antenna 2 peduncle, article 4 shorter than article 5.......................................................... 18 - Antenna 2 peduncle, article 4 longer than article 5.................................................. C. murrayae 18. Antenna 2 longer than antenna 1................................................................. C. alquirta - Antenna 2 shorter than antenna 1.................................................................. C. jonsoni 19. Telson with more than 15 recurved spines in two rows....................................................... 20 - Telson with less than or equal to 15 recurved spines in two rows............................................... 21 20. Pereopod 5 merus with seven to nine setae at posterior lobe........................................ C. benthophilus - Pereopod 5 merus with five plumose setae at posterior lobe............................................ C. bundegi 21. Head subequal in length to pereonites 1 + 2................................................................ 22 - Head longer than pereonites 1 + 2................................................................ C. volucola 22. Telson with 13 or 14 recurved spines........................................................... C. maculanigra - Telson with 9 or 10 recurved spines.............................................................. C. yuyatalay