Linopherus, de Quatrefages, 1866

Shimooka, Satoshi, Koyama, Akihiko & Jimi, Naoto, 2025, A New Species of Linopherus (Annelida: Amphinomidae) from Kyushu, Japan, Species Diversity 30 (1), pp. 91-98 : 96

Key to Species of Linopherus [Modified from Sun and Li (2016)]

1. Branchiae present from chaetiger 2 continuing to end of body............. L. reducta (Kudenov and Blake, 1985) ( USA, Pacific Ocean)

— Branchiae present from chaetiger 3 or 4..............2

2. Branchiae present from chaetiger 3..................3

— Branchiae present from chaetiger 4.................16

3. Eyes absent......................................4

— Eyes present, one or two pairs (may not be visible in fixed specimens)..................................5

4. Several pairs of branchiae until end of body................................. L. tripunctata (Kudenov, 1975) ( Mexico, Pacific Ocean)

— Branchiae present only on anterior chaetigers................... L. oligobranchia ( Wu, Shen, and Chen, 1975) (Paracel Islands, South China Sea)

5. First pair of eyes semicircular......................6

— First pair of eyes rounded..........................8

6. Posterior margin of prostomium bilobed, more than 40 pairs of branchiae.... L. beibuwanensis Sun and Li, 2016 ( China, South China Sea)

— Posterior margin of prostomium not bilobed, less than 40 pairs of branchiae..............................7

7. Six pairs of branchiae, caruncle absent....................................... L. fauchaldi San Martín, 1986 ( Cuba, Caribbean Sea)

— About 23 pairs of branchiae, caruncle present, small and rounded............... L. microcephala (Fauvel, 1932) ( Maldives, Indian Ocean)

8. Anterior lobe of prostomium conical, not expanded anteriorly............... L. kristiani Salazar-Vallejo, 1987 ( Mexico, Pacific Ocean)

— Anterior lobe of prostomium rounded, anteriorly expanded ................................................9

9. One pair eyes...................................10

— Two pairs of eyes................................11

10. Caruncle present, cirri of second chaetiger longer than others............... L. paucibranchiata (Fauvel, 1932) ( Egypt, Gulf of Suez)

— Caruncle absent, cirri of second chaetiger as long as others............. L. hirsuta ( Wesenberg-Lund, 1949) (Persian Gulf)

11. More than 20 pairs of branchiae present............12

— Maximally 16 pairs of branchiae present............15

12. Branchiae present only on anterior chaetigers.......13

— Branchiae present in all but first two and last few chaetigers..........................................14

13. Caruncle distinct, square pad like.............................................. L. ambigua ( Monro, 1933) ( Panama, Pacific Ocean)

— Caruncle indistinct, completely concealed by second chaetiger........................ L. littoralis sp. nov. ( Japan, Seto Inland Sea)

14. Caruncle absent, eyes inconspicuous................................... L. spiralis ( Wesenberg-Lund, 1949) (Persian Gulf)

— Caruncle present, eyes conspicuous.......................................... L. oculata (Treadwell, 1941) ( Panama, Pacific Ocean)

15. 13–16 pairs of branchiae present, caruncle present................... L. annulata (Hartmann-Schröder, 1965) ( Chile, Pacific Ocean)

— Maximally seven pairs of branchiae present, caruncle absent................ L. canariensis Langerhans, 1881 (Canary Islands, Atlantic Ocean)

16. More than 40 pairs of branchiae present, eyes distinct, caruncle absent......... L. acarunculata ( Monro, 1937) ( Maldives, Indian Ocean)

— Less than 10 pairs of branchiae, eyes absent, caruncle present.........................................17

17. Seven pairs of branchiae present, subdistally inflated (hastate) acicular chaetae absent................................................. L. minuta (Knox, 1960) ( New Zealand, Pacific Ocean)

— Less than seven pairs of branchiae present, subdistally inflated (hastate) acicular chaetae present...........18

18. Five or six pairs of branchiae present, dorsal cirri absent in branchial chaetigers, caruncle in deep pocket at posterior margin of prostomium, small and rounded.............................. L. abyssalis (Fauchald, 1972) ( Mexico, Pacific Ocean)

— Five pairs of branchiae present, dorsal cirri absent in branchial chaetigers, caruncle button-shaped................................... L. hemuli (Fauchald, 1972) ( Norway, Sognefjord)