Paratelecrinus conifer

Messing, Charles G., 2013, A revision of the genus Atelecrinus PH Carpenter (Echinodermata: Crinoidea), Zootaxa 3681 (1), pp. 1-43 : 33-34

Paratelecrinus conifer (AH Clark, 1908a)

Figure 14

Atelecrinus conifer AH Clark 1908a: 213, 214. AH Clark and AM Clark 1967: 818 –820, 832.

Holotype. Atelecrinus conifer , AH Clark, 1908a, USNM 22685, Albatross 3887, NE of Molokai, Hawai’i, 21.275ºN, 156.665ºW, 1009–1479 m, 17 Apr 1902.

Other material examined. MNHN IE- 2009-9004, SALOMON 2, CP-2180, NE of Tulaghi I., Solomon Islands, 08°48' S, 159°41' E, 708–828 m, 22 Oct 2004 (1 spec.).

Diagnosis. A species of Paratelecrinus in which the centrodorsal base bears short interradial adoral projections that terminate in a V-shaped notch and cirri in 15 columns (3 per radial area); peripheral sockets relatively small (to 0.8–0.9 mm tall); brachitaxes and proximal brachial pairs with strong, narrow synarthrial swelling; lateral margins of Ibr1 straight or converging; Iax2 rhombic, with narrow proximal angle and rectangular distal angle.

Redescription of the holotype ( Figure 14 a). Centrodorsal slightly convex conical; basal diameter 4.1 mm; HD 1.3; interradial margin projecting and with a V-shaped excavation; interradial ridges barely present. Apex with traces of obsolete cirrus sockets. Sockets in 15 crowded columns, three per radial area, not separated interradially, 0.8–0.9 mm tall; 4–5 sockets in lateral columns, 3 in midradial column.

Cirri ~LX, all broken. AH Clark (in AH Clark and AM Clark 1967) described the longest remaining piece as 19 segments, 35 mm long; c1–2 short; c3 LW ~1.5 and the following segments compressed without prominent distal ends, LW ~3.0.

Externally visible portion of basals gently arched and slightly swollen interradially, of roughly uniform height but with the aboral margin gently sinuous, forming a low complete ring separated interradially from centrodorsal by ligament bundle. Radials short, distal margin slightly concave, lateral margins slightly diverging; WL ~4.0–5.0; radial profile ~90º.

IBr2 and IIbr1–2 with moderately developed synarthrial tubercles and separated by well developed gaps. Ibr1 with slightly converging lateral margins and deeply V-shaped distal margin; WL 2.4. Iax2 rhombic with sharp proximal angle and rectangular (truncated and parallel-sided) distal angle; WL 1.0.

IIbr1 with exterior margin longer and slightly ridged; distal margin shallowly V-shaped; WL 2.0. IIbr2 almost triangular, longer exteriorly and wider distally; WL 1.1. IIbr3+4 longer interiorly, 2.2 mm across; WL 1.1; exterior lateral margin concave. IIbr5 and following few remaining brachials short and wedge-shaped; WL of br5 2.1. Syzygies at 3+4, 6+7, 9+10 and 12+13.

Distribution. Known from the Hawaiian Islands and Solomon Islands. Depth range: (possible) 708–1479 m; (constrained) 828–1009 m.

Remarks. The second specimen attributed to P. c o n i f e r, MNHN IE-2009-9004, is smaller than the holotype, with centrodorsal diameter 4.1 mm and HD 1.2. It is generally similar but differs as follows. Sides of centrodorsal straight rather than slightly convex (although projecting basal sockets make the centrodorsal base appear narrowed). Interradial projections much weaker; V-shaped excavations very shallow. Midradial margin straight, irregular or with small triangular projection. Cirri LXXXIII (none remaining), with lateral columns of sockets in each radial area separated from those of adjacent radial areas by narrow flat strip; two lateral columns with 6–7 sockets and central column with 4–5 sockets. Apex with weak ridges (remnants of apical sockets). Basals almost straight with no arch and without the distinct interradial gap between basals and centrodorsal. Radials shorter; WL 5.3–5.6; radial profile ~120°; sides of radials visible between bases of adjacent rays. IBr2 and IIbr1–2 with stronger, narrow synarthrial tubercles. Ibr1 well separated laterally, with distal margin more deeply V-shaped; WL 2.8. Iax2 rhombic, longer than wide; WL 0.8; distal angle rectangular. Adjacent IIbr1 separated interiorly above axil. IIbr2 as long as or slightly longer than wide; WL 0.95–1.0. IIbr3+4 with WL 1.0–1.3, 2.5 mm across. IIbr5 almost triangular; WL 1.9. IIbr6+7 present. All arms lost at br3 or br6. Long probolus Adidas TM visible between two adjacent rays.

Because P. c o ni fe r is known from only two specimens, the features that distinguish it from P. orthotriremis and P. telo , the only other species with cirri in 15 columns, might not remain useful when additional specimens are found. The shape of the axil in particular clearly varies with growth in atelecrinids, e.g., from hexagonal to rhombic in both P. c u b e n s i s and P. orthotriremis (Figures 10, 16). However, the proximal angle of the axil (and that of IIbr2) is sharper in P. conifer than in other species when similarly-sized specimens are compared.

Figures

FIGURE 14. Paratelecrinus conifer (A. H. Clark). Centrodorsal and ray bases in lateral view. a. USNM 22685 (holotype). b. MNHN IE- 2009 - 9004. Scale bars: 1 mm.