Rouxicrinus vestitus, Mironov, Alexandr N. & Pawson, David L., 2010

Mironov, Alexandr N. & Pawson, David L., 2010, A new genus and species of Western Atlantic sea lily in the family Septocrinidae (Echinodermata: Crinoidea: Bourgueticrinida), Zootaxa 2449, pp. 49-68 : 52-64

publication ID	https://doi.org/ 10.5281/zenodo.195174
DOI	https://doi.org/10.5281/zenodo.5694231
persistent identifier	https://treatment.plazi.org/id/03D98500-FFC6-FFC0-55DC-FBBF176E654B
treatment provided by	Plazi
scientific name	Rouxicrinus vestitus
status	sp. nov.

Treatment

Rouxicrinus vestitus View in CoL new species

Figures 1–10

Etymology: The species name is derived from Latin vestis, a garment, in reference to the covering of soft tissue on the secundibrachials.

Diagnosis: As for the genus.

Material examined: Five specimens, collected using the submersible Johnson-Sea-Link ( HBOI) on housed in the National Museum of Natural History, Smithsonian Institution, Washington DC, USA. Holotype: USNM catalogue number E00042699, specimen collected by D. Billett and G. Hendler during dive JSL-II- 1737 off Speightstown, Barbados, 13º15'06''N – 59º45'04''W, depth 747 m, 20 April, 1989. Two paratypes: (1) USNM catalogue number E00042707, specimen collected by D. Pawson and D. Billett during dive JSL-II- 1729 off Barbados, 13°15'30''N – 59°45'47''W, depth 876 m, 16 April 1989; (2) USNM catalogue number E00042700, specimen collected by C. Young and J. Miller during dive JSL-II-1731 off Barbados, 13°16'17''N – 59°45'24''W, 816 m, 17 April 1989. Other material: (1) USNM catalogue number 1021239, specimen collected by D. Pawson and D. Billett during dive JSL-I-2268 off Bahamas, Crooked Island Passage between Long Island and Crooked Island, 22°41'23''N – 74°21'18''W, depth 887 meters, 15 September 1988; (2) USNM catalogue number E0017898, specimen collected during cruise 6607 of RV Pillsbury, St. 394-1 off Fuerte Island, Colombia, 9°28'36''N, 76°26'18''W, 421–641 m, 16 July 1966.

Description: In life, all specimens with stalk white, calyx and Brs with light cream tint, Ps reddish purple.

HOLOTYPE. (Figures 1, 2, 4A,B,D,F, 5, 6). Complete specimen except two arms broken at IBr3 with two short isolated fragments only, total length from base of radix to distal top of crown 155 mm. Calyx regularly conical without angle between basal and radial rings; interbasal and interradial sutures conspicuous. Distal margin of RR U-shaped; distolateral corners of adjacent RR forming narrow triangular interradial projections separating bases of adjacent rays (Figure 1). Interradial calyx height 1.9 mm (including length of interradial projections); maximum and minimum calyx diameter 2.5 and 1.1 mm; ratio of BB to RR height 0.61; surface of BB, RR and IBrs smooth without ornamentation.

Tegmen with an axis of bilateral compression running from interradius AB to radius D, arising radially to distal margin of Br3, interradially to distal margin of Br1 or base of Br2. Some tegminal (oral?) plates of irregular shape visible in peristomial elevation. Top of prominent anal sac level with middle of Br3, 1.4 mm high.

Length of primibrachitaxis (IBr1+2ax) 2.5–2.6 mm; ratio of IBr1 to IBr2 height ~0.7; that of IBr1/RR 0.8. IBrs broader distally than proximally, much broader than long with sides slightly flattened into lateral flanges not continuing in free arm bases; IBr2 without interradial projection between neighboring IIBrs1.

FIGURE 1. Rouxicrinus vestitus new genus, new species, Holotype, USNM E00042699. A. Calyx with proximal parts of stalk and arms. Prominent anal sac visible between diverging arms. B. Stalk (parts of proxistele and mesistele) between 16th and 51st columnals. C. Stalk (part of mesistele) between 77th and 86th columnals. D. Stalk (dististele) between 121st columnal and root-like radix.

Length of complete free arms up to 23 mm, ends of arms and pinnules usually rolled inward. Secundibrachials 45 to 54 in number. Proximal pattern with IIBr1+2 3+4, and 8+9 (5 cases), 6+7, 7+8, 9+10 (1 case each). Beyond the third, positions of non-muscular joints irregular in median and distal free arms (types of joint usually indistinguishable in distalmost part) illustrated by three following examples (1) 11+12 18+19 20+21 27+28 34+35 39+40, (2) 14+15 18+19 24+25 30+31, (3) 16+17 22+23 29+30. Never more than 6 successive muscular articulations observed. Muscular brachial articulations having classical features, inner ligament areas with galleried stereom, and slightly oblique fulcral ridge ( Figure 4 View FIGURE 4 B). Transverse synarthry without symmorphy and with relatively wide fulcral ridge at IIBr1+2 ( Figure 4 View FIGURE 4 C). Ligamentary articulation of more distal IIBrs flat and smooth synostosis, except short culmen at mid-adoral margin ( Figure 4 View FIGURE 4 A).

IIBrs and Pns covered by transparent film of soft tissue; labyrinthic stereom with coarse meshes and many needle-like projections, producing a dissected and thorny surface, especially on distal Brs and Ps. Thorns lie along distal margin of Brs and Pns ( Figures 2 View FIGURE 2 B, 4D, 5F).

On one side of an arm, maximum number of Ps 15, every second or third Br bearing a P. P1 on Br7 on four arms, Br6 on two arms, Br8 on two arms and lost on two arms (arms broken at Brs3). P1 of 13–14 Pns; maximum length 6.2 mm. P2–P4 of 15–16 Pns, up to 7.5 mm in length. Muscular synarthry between Pn1 and Pn2 ( Figure 5 View FIGURE 5 D); with typical characters remaining visible up to Pn9.

Relative length of Pns variable, Pn2 shorter than Pn1 (ratio 0.8–0.9) in proximal Ps; Pn3 always much longer than Pn1 (ratio more than 1.3); in P2 and P4 of a given arm, ratios relative to Pn1 length decreasing from 1.35–1.43 for Pn3 to 0.8 (P2) or 1.1 (P4) for Pn13. Pns crescentic in cross section, not V-shaped, with thorns along distal margin ( Figure 5 View FIGURE 5 B–F). Each ambulacral groove bordered on both sides by rod-like spicules and spherical bodies of soft tissue (sacculi) ( Figures 2 View FIGURE 2 A, 5A); spicules 0.30–0.45 mm long, curved, widening at distal end, pointed proximally ( Figure 5 View FIGURE 5 A); some spicules (especially in base of proximal Ps) branching distally; each spicule covered by transparent soft tissue (lappet). Cover and side plates absent. Sacculi creamcoloured, embedded in soft tissue with diameter 0.07–0.09 mm. Lappets in brachial ambulacral grooves with rod-like spicules or thin lacy plates; sacculi more elongated than those in Ps. Genital pinnules not distinguishable morphologically.

Remaining proximal part of stalk (72 columnals) attached to aboral cup 44 mm long. Total stalk length from calyx to base of radix, ~ 128 mm, of 128–131 columnals, consisting of proxistele attached to calyx and two stalk fragments (Figures 1B–D).

Stalk diameter increases slightly from columnal 1 (1.0 mm) to 7 (1.1 mm), decreases to 0.8 mm between columnals 8 and 35 (Figure 1B), remains the same from 36 to 74 (~ 0.8–0.9 mm), and increases slowly beginning at 75 to 1.4 mm by columnal 130 (Figures 1C and 1D). Height increases from 0.1 to 1.5 mm between columnal 1 and 72, remains unchanged (~ 1.4–1.6 mm) from 73 to 107, increases to 1.9 between 108 and 122, and decreases to 0.8 mm between 123 and 128. Height/diameter ratio increases from 0.16 for columnal 16 to 1.68 on 72, with columnal 48 as long as broad (Figure 1B), and decreases to 0.58 between 73 and 128 (Figure 1C).

Proximal columnals are monolithic or with indistinct longitudinal sutures. Median constrictions of columnals slightly or moderately developed in mesistele (Figure 1C), disappearing in four distalmost columnals (Figure 1D). Flat circular synostoses in proxistele, ovoid synarthries with coarse fulcral ridge along smallest diameter in mesistele ( Figure 4 View FIGURE 4 E), circular synarthries with well developed fulcral ridge and large deep areola in dististele ( Figure 4 View FIGURE 4 F). Distal synarthries with pentagonal lumen (0.12 mm of facet diameter) and fulcral ridge of irregular relief ( Figure 4 View FIGURE 4 F). Root-like radix, well developed. Thick basal part of radix consists of numerous coalesced ossicles (Figure 1D); sutures almost invisible. Distal radicles long, very thin, attached to numerous grains of sand and foraminiferal tests ( Figure 6 View FIGURE 6 B).

PARATYPE 1, USNM E00042707 ( Figures 3 View FIGURE 3 , 4 View FIGURE 4 C,E, 9C) AND PARATYPE 2, USNM E00042700 ( Figures 7 View FIGURE 7 B, 9C). Calyx as in holotype, with interradial projections. Maximum calyx diameter 2.50 and 2.68 mm, minimum diameter 1.30 and 1.23 mm, height (including length of interradial projections) 1.55 and 1.88 mm, ratio of BB/RR height 0.56 and 0.62 ( Figure 3 View FIGURE 3 A). Tegmen reaching middle or proximal margin of IIBr2 interradially. Tip of prominent anal sac level with base of Br4 terminating in relative high and broad terminal prominences ( Figure 3 View FIGURE 3 C). Adoral triads of tube-feet each with high columnar base, especially developed in radii C and E ( Figure 3 View FIGURE 3 C). Columnar bases of triads as well as soft tissue near mouth contain thin lacy plates.

Length of IBr1+2ax 2.37 and 2.38 mm; ratio IBr1/IBr2 height ~0.65 and 0.66. All free arms incomplete in paratype 1 and two arms complete in paratype 2; length of complete arms 29 mm with up to 44–45 IIBrs. Most frequent proximal free arm pattern 1+2 3+4 10+11 (6 of 11 cases). Most frequent position of P1 on IIBr7 (14 of 17 cases). P1 with 13–14 Pns, P 4 and 7 with 15 Pns each. Maximum number of successive muscular articulations 9. Rudimentary gonads occur at the bases of the proximal Ps. Every gonad is covered by Pn1 and is invisible externally ( Figure 9 View FIGURE 9 C).

Both stalks complete, but broken into fragments. Total length of stalk from calyx to radix ~149.0 and 128.8 mm, total number of columnals 139 and 129. In paratype 1 diameter decreases from columnal 7 (1.30 mm) to 55 (0.84 mm), then increases slowly to 1.63 mm at columnal 138. In paratype 2 diameter decreases from columnal 7 (1.43 mm) to 36 (0.87 mm), then increases slowly to 1.43 mm at columnal 128. Maximum ratio height/diameter of columnals 1.5 (in 85–90th columnals) and 1.68 (in 91th columnal); 54th and 57th columnals as hight as broad. Constriction at mid-height (never in proxistele) slightly or moderately developed in columnals 59 to136 and 50 to 125, and absent in the three distalmost. Mesistele synarthries as in holotype; distal synarthries circular with shallow ligament fossae. Fulcral ridge in all columnals as in holotype ( Figure 4 View FIGURE 4 E). Long thin distal radicles attached to numerous grains of sand and foraminiferal tests ( Figure 3 View FIGURE 3 B).

SPECIMEN FROM BAHAMAS, USNM 1021239 ( Figures 7 View FIGURE 7 a, 8, 9A, B). Largest specimen with crown and stalk connected, ten arm fragments and two stalk fragments. Because this specimen differs significantly from the type specimens it is described in detail. Calyx conical, 2.20 mm high interradially; maximum and minimum diameters 4.12 and 2.30 mm; interbasal and interradial sutures conspicuous. BB/RR length ratio 0.69. Distolateral corners of RR not projecting interradially; adjacent primibrachs not separated. Surface of BB, RR and IBrs smooth and without longitudinal median convexity. Tegmen not compressed, high, rising interradially to Br4 or Br5. No visible ossicles on sides (in spaces between primibrachials). Top of prominent anal sac level with Br7, about 5 mm high. Ten short projections at top (Figure 8C).

Length of IBr1+2 3.87 mm; IBr1/IBr2 length ratio ~0.71; IBr1/R height ratio 1.4. IBrs broader distally than proximally, much broader than hight, their sides of slightly flattened into lateral flanges not continuing on to IIBrs. IBr2 without median prolongation.

All arms incomplete. Length of best preserved arm 50 mm having 55 Brs with 20 Ps on one side. Complete arm had about 95–100 Brs and 35 Ps on one side. Proximal pattern of free arms always 1+2 3+4 (10 cases), 3rd non-muscular articulation from Br8 to 14, 4th from Br13 to 21, 5th from Br17 to 27, 6th from Br24 to 35, variation range increasing from proximal to distal arm. Three arms with regeneration rudiments from Br7, 9 and 18. Maximum number of successive muscular articulations 9 before Br13 (2 cases) and 2 cases of 7 before Br11, number varying from 3 to 8 (mode 5) between Br10 and 30, decreasing beyond Br30 (mode 3). Longest arm fragment with distal end (53 Brs) never more than 4 successive muscular articulations (mode 3). Thorns lie along distal margin of Brs and Pns (Figures 8B, C).

P1 on Br7; in one case on Br6. On one side of an arm, every second or third Br bearing a P (Figure 8B). Minimum length of P1 11.2 mm with 16–20 Pns. Longest middle Ps of 31 Pns, up to 21 mm long. Most proximal and median Pns approximately equal in length; Pn3 usually not longer than Pn1. Pns crescentic in cross section with thorns externally along distal margin; distal Pns with lateral thorns. Each ambulacral groove bordered on both sides by rod-like spicules. Few sacculi were found only at the bases of proximal Ps. Small gonads are hidden under Pns1 ( Figure 9 View FIGURE 9 A,B).

Stalk incomplete. Part attached to calyx composed of 124 columnals, 245 mm long. Two fragments of distal mesistele of 6 and 11 columnals; combined length 47 mm. Proximal columnals are quinquepartite. Stalk diameter increases from columnals 1 (2.20 mm) to 6 (2.35 mm); decreases between 7 and 32 to 1.85 mm (Figure 8F, D, E), remains the same (about 1.84–1.93 mm) from 32 to 60, and increases very slowly from 61 to 124 (2.51 mm). Columnal height increases from columnal 1 (0.25 mm) to 57 (2.51 mm), remains unchanged (~ 2.51–2.65 mm) between 57 and 115, and slightly increases to 2.80 mm by 124. Height/width ratio increases from columnal 6 (0.16) to 57 (1.3); columnal 41 is as long as broad. Sizes and proportions of columnals in the two fragments are the same as in columnals 121–124 of the stalk attached to the calyx. Mesistele synarthries like in other specimens.

This largest specimen differs from the other three small specimens ( USNM E00042699, E00042707 and 1021239) in having more numerous Brs, Ps, Pns and columnals, a higher tegmen and shorter Pn3. These differences are most likely associated with age. However, some other differences may not be associated with age: interradial projections of calyx and large sacculi are present in the smaller specimens and lacking in the large one.

SPECIMEN FROM FUERTE ISLAND, COLOMBIA, USNM E0017898 ( Figure 9 View FIGURE 9 D).

FIGURE 8. Rouxicrinus vestitus new genus, new species, USNM 1021239. A. Calyx with proximal parts of stalk and arms. B. Pinnules 10 and 11 on the Br29 and Br31. C. Part of tegmen with anal sac. D. Stalk (median parts of mesistele) between 56th and 67th columnals. E. Stalk (distal parts of mesistele) between 107th and 118th columnals.

The specimen in poor condition. Colour light yellowish-grey to whitish. Probably specimen has been fixed in formalin. Calyx with low interradial projections (relatively lower, than in the type specimens). Maximum and minimum calyx diameter 3.64 and 2.33 mm, height 2.24 mm, ratio of BB/RR height 0.65. Tegmen reaching proximal margin of Br5 interradially. Top of prominent anal sac level with Br9. Wide terminal opening of anal sac has side position and not bordered by projections.

Length of IBr1+2ax 3.81 mm; ratio IBr1/IBr2 height 0.90. One of arms lost, other are incomplete. Best preserved arm consists of 24 Brs. Most frequent proximal free arm pattern 1+2 3+4 7+8 (3 of 5 cases). Most frequent position of P1 on Br7 (3 of 5 cases). Pn3 longer than Pn1. Sacculi not observed because of poor condition of ambulacral grooves. Developed gonads are clearly distended ( Figure 9 View FIGURE 9 D).

Stalk incomplete. Remaining proximal part of stalk (47 columnals) attached to aboral cup 42 mm long. A fragments of mesistele of 13 columnals. Some of proximal columnals compound. Tip of the stalk not tapering upwards. Stalk diameter decreases from columnals 1 (2.33 mm) to 23 (1.54 mm), and increases slowly from 24 to 47 (1.74 mm). Maximum stalk diameter in the mesistele fragment 1.83 mm. Columnal 38 is as long as broad; maximum height/width ratio 1.45 in the mesistele fragment.

This specimen differs significantly from the small (type) specimens in having whitish arms, a higher tegmen, different brachial patterns, large gonads, tip of stalk not tapering, and in lacking developed interradial projections of RR and terminal projections on the anal sac.

Distribution: Western tropical Atlantic, off Barbados, Fuerte Island ( Colombia) and Bahamas, in depths of 421 to 887 m. This depth range is considerably shallower than previous records of species of Septocrinidae . Septocrinus is known from 5180–5190 m, Zeuctocrinus from 2000 to 6785 m.