Ophiuroidea, Gray, 1840

Granja-Fernández, Rebeca, Hendrickx, Michel E., Rangel-Solís, Pedro Diego & López-Pérez, Andrés, 2023, Deep-sea Ophiuroidea (Echinodermata) collected during the TALUD cruises in western Mexico, Zootaxa 5259 (1), pp. 1-71 : 11-13

Key to the identification of the genera and species of deep-sea Ophiuroidea collected during the TALUD cruises in western Mexico

1 Dorsal disc with naked skin and external ossicles. DAP and VAP absent......................................... 2

1’ Dorsal disc without naked skin and external ossicles. DAP and VAP present...................................... 4

2 Up to 3–4 ArSp, serrated but not hooked............... genus Astrodia , Astrodia excavata (Lütken & Mortensen, 1899)

2’ More than three ArSp, modified as hooks................................................... genus Asteronyx , 3

3 Ventral interradii with some granule-shaped epidermal ossicles proximally. Genital slits oval, restricted to middle-distal part of the interradius, covering approximately 3/4 of the interradius. OSh rounded triangular. Madreporite not evident. Oral papillae spiniform............................................................. Asteronyx longifissus Döderlein, 1927

3’ Ventral interradii with circular-shaped epidermal ossicles. Genital slits round, restricted to proximal part of the interradius, covering approximately 1/6 of interradius. OSh not evident. One small circular madreporite. Oral papillae granule-like....................................................................... Asteronyx loveni Müller & Troschel, 1842

4 Dorsal disc with disc scales, obscured by skin and covered with fine granules.......................................................................... genus Ophiernus , Ophiernus adspersus annectens Lütken & Mortensen, 1899

4’ Dorsal disc with scales, visible and not obscured by skin...................................................... 5

5 Dorsal disc with scales only............................................................................ 6

5’ Dorsal disc with scales and granules, spines............................................................... 24

6 Dorsal disc scales depressed............................. genus Histampica , Histampica cf. duplicata ( Lyman, 1875)

6’ Dorsal disc scales not depressed......................................................................... 7

7 Jaws bearing more than three oral papillae at each side....................................................... 8

7’ Jaws bearing three oral papillae at each side............................................................... 19

8 Dorsal disc with diminutive scales, naked appearance........................................................ 9

8’ Dorsal disc with scales, appearance not naked............................................................. 10

9 Jaws bearing 6–7 oral papillae at each side, distalmost lanceolate and the largest. Up to three ArSp, approximately two arm segments in length. Two TSc, adradial slender and elongated, abradial rounded........................................................................................ genus Ophiochiton , Ophiochiton cf. fastigatus Lyman, 1878

9’ Jaws bearing 2–3 oval AdShSp and 2AdShSp, BSc elongated, TPa numerous, elongated, different sizes. Up to five ArSp, approximately one arm segment in length. Two TSc, adradial lanceolate and extremely elongated crossing the abradial TSc, abradial pointed....................................... genus Ophiopsila , Ophiopsila californica A.H. Clark, 1921

10 Few pairs of tentacle pores, restricted to proximal arm segments. Arm combs absent............................... 11

10’ Numerous pairs of tentacle pores, present in most arm segments. Arm combs present.............................. 14

11 Tentacle pores obvious on two proximal arm segments... genus Ophiomusa , Ophiomusa lymani ( Wyville-Thomson, 1873)

11’ Tentacle pores obvious on three or more proximal arm segments........................... genus Ophiosphalma , 12

12 Tentacle pores obvious on up to 3–5 proximal arm segments. One pointed abradial and 1–2 adradial TSc. Up to 12 ArSp............................................................ Ophiosphalma glabrum (Lütken & Mortensen, 1899)

12’ Tentacle pores obvious on up to three proximal arm segments. One round TSc. Up to three ArSp..................... 13

13 Primary plates round, conspicuous. RS covering 1/3 of the disc radius. OS spearhead-shaped, rounded angles............................................................................ Ophiosphalma jolliense ( McClendon, 1909)

13’ Primary plates not conspicuous. RS covering 1/2 of the disc radius. OS rhomboidal-shaped, right angles......................................................................... Ophiosphalma variabile (Lütken & Mortensen, 1899)

14 Disc rounded....................................................................................... 15

14’ Disc pentagonal..................................................................................... 17

15 Rays of integument in RS and project from the arms................. genus Ophiura , Ophiura flagellata ( Lyman, 1878)

15’ Center of the disc without interradial rays of integument..................................................... 16

16 RS triangular. VAP almost hemispherical, widely separated. Genital papillae pointed. Jaws bearing four oral papillae at each side, IPa rectangular, 2IPa semi-oval. Three ArSp. First tentacle pore with 1–2 oval TSc....................................................................................... genus Ophiocten , Ophiocten hastatum Lyman, 1878

16’ RS shields oval. VAP diamond-shaped, separated. Genital papillae papilliform. Jaws bearing 6–7 oral papillae at each side, IPa semi-rectangular, 2IPa semi-quadrangular. 3–4 ArSp. First tentacle pore with 8–9 elongated TSc................................................................. genus Ophiuroglypha , Ophiuroglypha irrorata irrorata ( Lyman, 1878)

17 RS tuberculous, very swollen. DAP with a prominent longitudinal keel............................................................................................... genus Stegophiura , Stegophiura ponderosa ( Lyman, 1878)

17’ RS not tuberculous and not swollen. DAP without a prominent longitudinal keel............... genus Amphiophiura , 18

18 Disc with a central depression, covered with irregular oval scales. Primary plates conspicuous. Genital papillae minute, pointed. Arm combs with rounded papillae. Jaws bearing five oral papillae at each side, TPa two. Three ArSp, pointed often widened at the tip........................................................... Amphiophiura oligopora (H.L. Clark, 1913)

18’ Disc swollen without a central depression, covered with irregular, prominent, inflated right-angled plates. Primary plates not conspicuous. Genital papillae small, quadrangular.Arm combs with pointed or rounded-squared papillae. Jaws bearing 4–5 oral papillae at each side, TPa 1–2. 3–4 blunt ArSp.................... Amphiophiura superba (Lütken & Mortensen, 1899)

19 Ventral interradius covered with granules.................................................................................................... genus Amphichondrius , Amphichondrius granulatus (Lütken & Mortensen, 1899)

19’ Ventral interradius covered with scales/integument......................................................... 20

20 AdShSp larger than all other oral papillae. BSc absent......... genus Amphipholis , Amphipholis pugetana ( Lyman, 1860)

20’ AdShSp same size as all other oral papillae. BSc present...................................... genus Amphiura , 21

21 One TSc.............................................................. Amphiura carchara H.L. Clark, 1911

21’ Two TSc........................................................................................... 22

22 Dorsal disc only with scales. Ventral interradius with imbricated scales. Primary plates conspicuous...................................................................... Amphiura (Amphiura) diomedeae Lütken & Mortensen, 1899

22’ Dorsal disc with thickened integument and scales. Ventral interradii with thickened integument. Primary plates inconspicuous .................................................................................................. 23

23 Dorsal disc mostly only with integument, imbricating scales only around RS. Up to 6–7 flat tipped ArSp...................................................................................... Amphiura arcystata H.L. Clark, 1911

23’ Dorsal disc with integument only distally, imbricated scales on most of disc. Up to 5–6 blunt tip ArSp............................................................................ Amphiura gymnogastra Lütken & Mortensen, 1899

24 Dorsal disc with scales, spines and/or granules............................................................. 25

24’ Dorsal disc with scales and spines....................................................................... 30

25 Dorsal disc with scales and granules. Without striated LAP................................................... 26

25’ Dorsal disc with scales, granules, and spines. With striated LAP............................... genus Ophiolimna , 29

26 Detached granules on dorsal disc leave a fingerprint as a depression in each scale when the specimens are roughly handled............................................. genus Ophiomitra , Ophiomitra granifera Lütken & Mortensen, 1899

26’ Detached granules on dorsal disc do not leave a fingerprint as a depression in each scale when the specimens are roughly handled......................................................... genus Ophiophthalmus and Ophiacantha , 27

27 Distal edge of DAP with a conspicuous row of pointed granules............... Ophiophthalmus normani ( Lyman, 1879)

27’ Distal edge of DAP without a conspicuous row of pointed granules............................................ 28

28 Jaws bearing six oral papillae at each side, AdShSp elongated. 6–7 smooth ArSp. Two oval TSc........................................................................................... Ophiacantha diplasia H.L. Clark, 1911

28’ Jaws bearing 6–7 oral papillae at each side, AdShSp rounded. Up to 4–5 smooth, flattened ArSp. First seven tentacle pores with two TSc, subsequent pores with one lanceolate TSc...................... Ophiacantha quadrispina (H.L. Clark, 1917)

29 Jaws bearing five oral papillae at each side, one IPa. DAP triangular. Up to 7–8 smooth, pointed ArSp. One lanceolate TSc......................................................................... Ophiolimna bairdi ( Lyman, 1883)

29’ Jaws bearing 5–6 oral papillae at each side, two IPa. DAP hexagonal. Up to 6–7 slender, blunt ArSp. First 2–3 tentacle pores with two TSc, subsequent pores with one oval TSc........................ Ophiolimna phragma ( Ziesenhenne, 1940)

30 TPas absent........................................................................................ 31

30’ TPas present as cluster................................................................................ 36

31’ One or no papilla ventral to teeth...................................................... genus Ophiacantha , 32

31’ Two oral papillae (IPa) at the apex of jaw, ventral to teeth.................................................... 35

32 Arms with noded appearance................................ Ophiacantha moniliformis Lütken & Mortensen, 1899

32’ Arms without noded appearance........................................................................ 33

33 DAP bell-shaped with rounded edges............................... Ophiacantha costata Lütken & Mortensen, 1899

33’ DAP triangular with rounded edges..................................................................... 34

34 Dorsal disc with scattered and short multifid spines. RS semi-circular and not covered with multifid spines. Jaws bearing three oral papillae at each side, AdShSp lanceolate, LOPa one. Up to 7–8 serrated ArSp, approximately two arm segments in length. TSc almost as long as VAP............................................ Ophiacantha eurypoma H.L. Clark, 1911

34’ Dorsal disc totally covered with slender multifid spines. RS slender and covered with multifid spines. Jaws bearing 3–4 lanceolate oral papillae at each side, AdShSp flat, LOPa 1–2. Up to six smooth, blunt ArSp, almost one arm segment in length. Pointed TSc, shorter than the VAP................................ Ophiacantha pacifica Lütken & Mortensen, 1899

35 Dorsal disc with scales (largest in the center) and spines surrounding the margin of the disc and the RS. AdShSp shortest, not serrated, rounded. DAP not fragmented. Up to five pointed ArSp. One rounded TSc.... genus Dougaloplus , Dougaloplus sp.

35’ Dorsal disc with scales and scattered small spines mostly present around the margin of the disc. AdShSp largest, slightly serrated, rectangular. Some DAP fragmented in 2–3 pieces. Up to three blunt-tip ArSp. Two oval TSc.................................................................... genus Ophiocnida , Ophiocnida californica Ziesenhenne, 1940

36 Absence of oral papillae. Presence of 24–27 TPas. DAP not surrounded by symmetrical accessory plates.......................................................... genus Ophiothrix , Ophiothrix galapagensis Lütken & Mortensen, 1899

36’ Presence of oral papillae. Presence of numerous TPas. DAP surrounded by symmetrical accessory plates................................................................................................. genus Ophiopholis , 37

37 Dorsal disc (including RS) covered with scales and short multifid spines, those on the margin and the center elongated. Ventral interradii with elongated multifid spines. Up to 4–5 ArSp, first dorsalmost rudimentary................................................................................................... Ophiopholis bakeri McClendon, 1909

37’ Dorsal disc (usually absent from the RS) covered with scales and long spines, those on the margin more numerous. Ventral interradii with scales and some short spines. Up to 6–7, first dorsalmost the longest.................................................................................................... Ophiopholis longispina H.L. Clark, 1911