Adelatelecrinus vallatus, Messing, Charles G., 2013

Messing, Charles G., 2013, A revision of the genus Atelecrinus PH Carpenter (Echinodermata: Crinoidea), Zootaxa 3681 (1), pp. 1-43 : 19-21

Adelatelecrinus vallatus new species

Figure 8

Holotype. Solomon Islands: MNHN IE- 2009-9003, SALOMON 2 cruise, CP-2246, W of Vella Lavella I., 07°43' S, 156°25' E, 664–682 m, 1 Nov 2004.

Paratypes. Solomon Islands: MNHN IE- 2009-9002, SALOMON 2 cruise, CP-2211, SW of Choiseul I., 07°36'S, 157°42' E, 313–387 m, 26 Oct 2004 (1 spec.); MNHN IE- 2012-843, SALOMON 2 cruise, CP-2245, W of Vella Lavella I., 07°43'S, 156°26' E, 582–609 m, 1 Nov 2004 (1).

Other material examined. Solomon Islands: MNHN IE- 2007-7713, SALOMON 1 cruise, CP-1802, off Guadalcanal I., 09°31.1’S, 160°35.0’E, 245–269 m, 2 Oct 2001 (1); MNHN IE- 2007-5946, EXBODI cruise, CP- 3808, off Ile Toupeti, 21°43'S, 166°39'E, 598-645 m, 5 Sep 2011 (1). MNHN IE- 2007-5469, EBISCO cruise, CP- 2651, sud-est Fairway, 21°29'S, 162°36'E, 883-957 m, 23 Oct 2005 (1).

Diagnosis. A species of Adelatelecrinus with brachitaxes laterally flattened and apposed with no gap between adjacent rays; lateral flattening continuing on IIbr1.

Etymology. From the Latin vallum, a rampart or palisade. The specific epithet means surrounded with a rampart or wall, reflecting the characteristic flattened and apposed sides of the ray bases.

Description of the holotype ( Figure 8 a). Centrodorsal conical, tapering from base (although base partly straight-sided in some views), 4.0 mm across base, 5.4 mm high; HD 1.35; apex rounded with traces of obsolete sockets. Cirrus sockets XXIX, 3 per column (one with 2) in 10 columns. Fulcral tubercles moderately developed, rounded triangular in profile. Interradial ridges reduced to slight swelling, not reaching beyond basalmost socket in each radial area. Centrodorsal margin straight or very shallowly concave across radial areas, flat or very slightly Vshaped interradially. Centrodorsal/basal suture close or with short, slit-like interradial gap. Longest remaining attached cirrus fragment of 18 segments, 36 mm long (distal portion missing); c1–3 short; c4 squarish; following cirrals becoming longer and compressed with distally projecting adoral margin; c9–10 longest, LW 4.3; following segments slightly shorter. Externally visible interradial portion of basals large, irregularly triangular, almost flat, strongly tapering and barely in contact laterally. Radials with diverging lateral margins; WL 2.3; radial profile 70º; distal margin very broadly and shallowly U-shaped. IBr2 laterally flattened and apposed with no gap between adjacent rays, and with weak narrow synarthrial swelling. Ibr1 oblong, with lateral margins concave—initially converging but then diverging as distolateral, flat-sided flange continuous with flat-sided lateral margin of Iax2; WL 1.6; distal margin shallowly V-shaped. Iax2 hexagonal with diverging, thickened and flat-sided lateral margins apposed against adjacent axil; distal angle rounded; WL 1.3. IIbr1–2 well separated interiorly with well-developed gap. IIbr1 longer and flat-sided exteriorly; WL 1.6. IIbr2 irregularly quadrate, longer exteriorly; proximal margin shallow V-shaped; WL 1.3. IIbr3+4 thickened and in contact interiorly, WL 1.4; diameter 2.3 mm. IIbr5 almost triangular, WL 2.8. Brachials following 6+7 strongly wedge-shaped, with small alternating articular tubercles; WL 1.6. Syzygies at 6+7, 9+10; one arm with 6+7, 10+11, and one with 6+7, 11+12, 16+17, 21+22.

Paratypes. The paratypes differ slightly as follows. Centrodorsals of both taper from the base. In MNHN IE- 2009-9002, centrodorsal tip lost; basal diameter 3.9 mm; midradial basal margin concave or flat; interradial margin slightly projecting and V-shaped; no gap between basals and centrodorsal. Cirri XXV, none retained; 2–3 functional and 1–2 obsolete sockets per column; socket fulcral tubercles low to moderate. Externally visible interradial portion of basals rhombic, barely inflated. Proximal ray ossicles similar to those of holotype but proportionally slightly shorter, e.g., WL of radials, Ibr1, Iax2, IIbr1 and middle brachials 2.5, 1.4, 1.8, 2.0, and 1.3– 1.5, respectively. Syzygies at 3+4, 7+8 on 5 arms; 3+4, 6+7 on 3 arms; next syzygy at 10+11 (5 arms), 11+12 (2) or 12+13 (1); following at intervals of 2–3 articulations. In MNHN IE 2012-843, centrodorsal 5.5 mm tall, 4.2 mm across base; HD 1.3; interradial ridge a short, low swelling; interradial margin of centrodorsal straight; no gap between basals and centrodorsal. Cirri XXXI, none retained, in 3 functional sockets per column (1 column with 4). Externally visible interradial portion of basals triangular, slightly swollen, some not reaching adjacent basal. IBr2 and IIbr1 not as strongly flat-sided as in other two specimens, but still apposed and without gap. Lateral flange of Iax2 not as strong. Proximal ray ossicles proportionally shorter than both preceding specimens, e.g., WL of radials, Ibr1, Iax2, and IIbr1 2.8, 1.9, 1.0 and 2.3, respectively. Syzygies at 3+4, 6+7 and 9+10 or 10+11. Weak articular tubercles present on IIbr7 and following ossicles.

Description of other specimens. MNHN IE- 2007-5946 ( Figure 8 b). Large specimen. Centrodorsal conical, 4.1 mm across base, 6.3 mm tall; HD 1.5; tapering from base; apex rounded conical with traces of obsolete sockets. Cirrus sockets XXXI, 3 per column (one with 4). Fulcral tubercles low; sockets elongated along oral-aboral axis. Interradial base of centrodorsal lacking ridge; instead, a slight depression between two short, low swellings. Midradial base of centrodorsal distinctly depressed. Centrodorsal margin straight or very slightly V-shaped interradially. Centrodorsal/basal suture close. Externally visible portion of basals are wide, low triangles; each interradial portion slightly projecting and spanning width of two low interradial swellings on centrodorsal; strongly tapering laterally and not in contact laterally. Ray bases similar to those of holotype, apposed and flattened laterally, with rhombic gap interiorly between IIbr1 and IIbr2. Radial WL 2.2; radial profile ~70º; Ibr1 WL 1.6; Iax2 with weaker lateral flanges than in holotype; WL 1.2. IIbr3+4 WL 1.2; diameter 2.4 mm.

MNHN IE- 2007-7713. Small specimen. Centrodorsal conical, 2.3 mm across base, 3.0 mm tall; HD 1.3; base straight-sided; apex rounded conical with traces of obsolete sockets; midradial margin gently concave; interradial margin flat; interradial ridges low but sharp, reaching just beyond first socket. Cirri XXIV, 2–3 per column in 10 columns; bases of several cirri retained; c1–3 short, c4 with LW 1.6; c4 and c5 of more apical cirrus with LW 2.8 and 3.8, respectively. Externally visible interradial portion of basals triangular, slightly inflated as continuation of centrodorsal ridge, becoming somewhat narrower and parallel-sided laterally. Centrodorsal/basal suture well defined but with no distinct gap. Radials with diverging lateral margins, WL 1.3; profile 70°. IBr2 flat-sided, apposed, with no synarthrial tubercles or gap between adjacent IBr2. Ibr1 with slightly concave lateral margins and with broadened flange restricted to distolateral corner; more rounded aborally than in larger specimens; distal margin slightly concave; WL 1.4. Iax2 hexagonal with short diverging lateral margins expanded as flat-edged flange apposed against adjacent axil; WL 1.2. IIbr1 longer and flattened exteriorly, with distal margin only slightly concave; WL 1.6. IIbr2 pentagonal, longer exteriorly, with small interior gap between adjacent IIbr2; WL 1.2. IIbr3+4 1.3 mm across; WL 1.1. IIbr5 wedge-shaped; WL 1.7. One arm lacking IIbr3+4; IIbr3 wedge-shaped, IIbr4 parallelogram-shaped, IIbr5 wedge-shaped, followed by IIbr6+7; all other arms with syzygies at 3+4, 6+7; additional syzygies retained at 10+11, 15+16.

Distribution. Currently known only from the Solomon Islands in 387–664 (possibly 313–682) m.

Remarks. This species is placed in Adelatelecrinus because it shares with the type species, Ad. sulcatus , similar centrodorsal structure and the presence in at least some cases of a small, interradial slit between the centrodorsal and basals. It differs in having brachitaxes with distinctly broadened, flat-sided and apposed lateral margins.

Although the small specimen, MNHN IE-2007-7713, was collected with Ad. sulcatus , it is identified here as Ad. vallatus as it shares with this species closely apposed adjacent brachitaxes and the characteristically broadened and flat-sided axils. However, this assignment is tentative. Two species of atelecrinid have never previously been collected in the same sample. Also, the broadened axil might be a feature of small Ad. sulcatus lost with growth, similar to the ontogenetic changes in axil shape seen in Paratelecrinus cubensis and P. o r t h o t r i re m u s described below, even though the trait is retained in large Ad. vallatus .

Figures

FIGURE 8. Adelatelecrinus vallatus new species; centrodorsal and ray bases in lateral view. a. MNHN IE- 2009 - 9003 (holotype), b. MNHN cat no. IE- 2007 - 5946. Scale bars: (a) 1 mm; (b) 2 mm.