Belonometra kogoi Obuchi and Omori, 2015

Obuchi, Masami, 2020, Shallow-water Comatulids (Echinodermata: Crinoidea: Comatulida) of the Ashizuri-Uwakai Sea, Shikoku Island, Southern Japan, Species Diversity 25, pp. 309-328 : 322-324

30. Belonometra kogoi Obuchi and Omori, 2015 [Japanese name: Matsuba-umishida]

Morphology. Centrodorsal low hemispherical, 7.6– 8.0 mm across; polar area 0.2–0.3 times of centrodorsal diameter. Cirri delicate, numerous, XC– CXXX, up to 22 segments, 30 mm long, much crowded; peripheral cirri longer than apical ones, about twice; distal end of segments flared, overlapping base of following; c5–10 longest, L/ W 3.0; no aboral ornamentation excepting opposing spine . Radials invisible. IBr series composed of 2 ossicles; each ray separated well. Arms 10, up to 190 mm long, flexible; all brachials broader than long; first arm syzygy at br 3+4; distal intersyzygial interval 3. Comparative pinnule length P 1 =P 2 <P 3 =P 4>P 5; pinnules, except most-proximal two, remarkably slender, with longest segments L/W more than 3.0. Disk globular, smooth, three to four times as wide as centrodorsal.

Posture. Hiding on underside of overhangs, but sometimes fully exposed, with arms in multidirectional posture.

Coloration in life. Uniformly dark yellow to black, faded in distal arms and pinnules.

Distribution. Ashizuri-Uwakai Sea and Okinawa Island, at depths deeper than 20 m ( Obuchi and Omori 2015).

Remarks. The monospecific genus Belonometra was recently established on the basis of the specimens from the Ashizuri-Uwakai Sea ( Obuchi and Omori 2015). It is peculiar in having a large size for the family, numerous cirri and slender pinnules.

Morphological Key to Shallow-water Comatulids of the Ashizuri-Uwakai Sea

1. Terminal combs present on pinnules, at least on proximal ones..................................... 2

– No terminal combs on pinnules.................... 18

2. First arm syzygy at br 1+2 ........................... 3

– First arm syzygy at br 3+4 ............................ 4

3. All division series composed of 2 ossicles; comb teeth confluent with margin of segments closest to arm............................. Comatella stelligera

– Division series composed of 2 and 4(3+4) ossicles; comb teeth confluent with margin of segments away from arm........................ Phanogenia distincta

4. Small interradial plates present between basal rays; arms more than 80, often exceeding 100.. Comaster nobilis

– No interradial plates; arms less than 60............... 5

5. Terminal combs consisting of large triangular teeth contacted to neighbor one at base; proximal segment with large saucer-like transverse tooth; terminal segment with discrete tooth....................... 6

– Terminal combs consisting of teeth separated from neighbor one; proximal segment with low tooth, or transverse bridge formed by fusion of paired teeth; teeth diminished or fused into sharp tip at terminal segments....................................... 10

6. Radials fully concealed by centrodorsal with row of well-developed cirri......... Comanthus wahlbergii

– Radials exposed, at least at distal margin; centrodorsal small with few cirri............................ 7

7. Combed pinnules restricted to one third of arms..... 8

– Combed pinnules present on distal arms.............. 9

8. No cirri in mature specimens; lengths of radials almost half of centrodorsal diameter.... Comanthus suavia

– Few cirri present; radial narrowly exposed... Comanthus scintillus

9. Middle segments of distal pinnules with fringing spines on distal end................... Comanthus gisleni

– Middle segments of distal pinnules smooth.......................... Comanthus parvicirrus

10. Cirri stout, more than XV; radials perfectly concealed by large centrodorsal; pinnule combs always with unpaired tooth............................... 11

– Cirri weak, less than XV or totally absent, arranged on small centrodorsal with gap; radials exposed at least partly; pinnule combs with paired or unpaired tooth ............................................ 13

11. IIIBr series composed mostly of 2, partly 4(3+4); arm length often exceeding 200 mm ............................ Anneissia intermedia

– IIIBr series of 4(3+4); arm length less than 180 mm ... 12

12. More than 30 arms; centrodorsal hemispherical, with two to three rows of cirri; pinnules with smooth keel on basal segments.............. Anneissia japonica

– Arms not more than 30; centrodorsal discoidal, with one, partly two rows of cirri; pinnules with everted and spiny basal segments............. Anneissia solaster

13. Terminal combs present as far as P 8; proximal segment of combs with paired discrete tooth or transverse bridge formed by fusion of them........................ Clarkcomanthus mirabilis

– Terminal combs restricted to some proximal pinnules; proximal segment of combs with tooth diminished in size...................................... 14

14. Terminal combs with sharp tip formed by fusion of some segments and teeth...................... 15

– Terminal segments of pinnule comb not fused, with small discrete teeth................................ 17

15. Pinnule combs with peg-like secondary tooth; disk remarkably large, more than ten times as large as centrodorsal............... Clarkcomanthus mirus

– Pinnule combs unpaired; disk less than eight times as wide as centrodorsal.......................... 16

16. Medium sized with arm length exceeding 100 mm; comb present as far as P 4; dark mid-aboral line on arms.............. Clarkcomanthus comanthipinna

– Small sized with arm length less than 100 mm; comb present to P 1, rarely to P 2; arm banded with red and white...................... Clarkcomanthus exilis

17. Segments of proximal pinnules broader than long; distal pinnules much shorter than P 1; no mid-aboral line on arms................. Clarkcomanthus littoralis

– Middle segments of pinnules on division series longer than broad; distal pinnules almost as long as P 1; pale mid-aboral line on arms....................... Clarkcomanthus albinotus

18. IBr series united by syzygy....................... 19

– IBr series not united by syzygy..................... 20

19. More than 20 arms........... Catoptometra magnifica

– Less than 19 arms.............. Catoptometra rubroflava

20. At least some cirrus segments with a pair of tubercles or single transverse ridge on aboral side............ 21

– Cirrus segments with single spine or tubercle, or without aboral ornamentation......................... 25

21. Cirri long, exceeding one third of arm length, with more than 60 segments...... Pontiometra andersoni

– Cirri short, less than one fifth of arm length, with less than 50 segments............................. 22

22. P 2 much stout, recurved, horn-like.... Cenometra bella

– P 2 not so different from other proximal pinnules...... 23

23. More than 30, usually 50–80, arms; medium to large sized with arm length exceeding 150 mm ........................... Basilometra boschmai

– Less than 30 arms; small sized with arm length usually less than 120 mm ............................. 24

24. P 1–3 stiff, spine-like; up to 20 arms... Alisometra owstoni

– P 1–3 not stiffened; usually 10 arms... Iconometra japonica

25. More than 10 arms.............................. 26

– Only 10 arms.................................... 27

26. Division series beyond IIBr composed of 4(3+4); brachials extremely short, W/L more than six, with articulation almost parallel Himerometra magnipinna

– All division series of composed 2 ossicles; brachials not so short...................... Lamprometra palmata

27. Pinnules with longitudinal ridge on aboral side, triangular in cross section.................... Tropiometra afra macrodiscus

– Pinnules without longitudinal ridge, cylindrical in cross section...................................... 28

28. Pinnules much slender; large sized with arm length exceeding 150 mm .............. Belonometra kogoi

– Pinnules not so long; small sized with arm length less than 100 mm ................................ 29

29. Proximal pinnules conspicuously knobbed due to segments distally everted; P 1 longer than P 3 ................................ Antedon serrata

– Proximal pinnules smooth; P 3 enlarged, longer than P 1 ........................... Dorometra parvicirra