Circeaster arandae, Mah, 2006

Mah, Christopher L., 2006, Phylogeny and biogeography of the deep-sea goniasterid Circeaster (Echinodermata, Asteroidea, Goniasteridae) including descriptions of six new species, Zoosystema 28 (4), pp. 917-954 : 934-935

Circeaster arandae n. sp.

( Fig. 5 A-C)

HOLOTYPE. — Madagascar. 13°48.8’S, 47°29.4’E, 1800- 2000 m, 27.II.1975, 1 dry spec., R = 9.5 cm, r = 2.2 cm ( MNHN EcAs 11727).

PARATYPES. — Madagascar. 13°40.3’S, 47°32.5’E, 1600- 1725 m, 28.II.1975, 1 dry spec., R = 10.4 cm, r = 2.3 cm ( MNHN EcAs 11728).

New Caledonia. 24°28’S, 168°08’E, 2160 m, 3.IX.1985, 1 dry spec., R = 8.9 cm, r = 1.9 cm ( MNHN EcAs 11729).

ETYMOLOGY. — This species is named for my colleague Danielle Aranda from Rio del Valle Junior High in Oxnard, California, in honour of her dedication to science education.

DISTRIBUTION. — New Caledonia to Madagascar. 1600- 2160 m.

DIAGNOSIS. — R /r ≥ 4.0. Circeaster with relatively small disk, arms relatively narrow. Abactinal arm plates bare, enlarged 3-5 times disk plates. Transition between disk and arm plates abrupt. Marginal plates with single prominent sharp spine, with secondary spinelets. Marginal plates on disk with high density of sharp spinelets. Ventrolateral edge of inferomarginal plates with several sharp spinelets. Adambulacral with furrow spines, 1-2 paddle-like pedicellariae, subambulacral spine, enlarged. Tips roughened/fluted adjacent to pedicellariae. Spinelets cover adambulacral, actinal plates.

APOMORPHY LIST. — Nodes 21 to 16: 2.11, SM contact with abactinal plates, curved to straight; 4.1, subambulacral spine, single, enlarged; 4.2, abradial to furrow spines; 6.2, arms narrow.

Nodes 22 to Circeaster arandae n. sp.: 2.4, superomarginal spines present; 2.5, inferomarginal spines present; 2.8, IM accessories, few, scattered; 2.10, spinelets present as peripheral accessories on marginal plates.

DESCRIPTION

Disk relatively small. Interradial arcs linear to curved. Abactinal disk plates weakly convex, largely bare; many with granules or moderate-sized tubercles. Abactinal disk plates round to polygonal. Size and shape largely homogeneous, although plate size decreases closer to superomarginals. Granules and nubbin-like tubercles most heavily concentrated on central disk region, decreasing in abundance closer to the edge of the disk, base of arm.Tubercles absent from New Caledonian specimen, present only on Indian Ocean specimens.When present, three to five coarse low-lying to hemispherical granules; angular to polygonal in cross-section, scattered on disk surface but absent from arm plates and peripheral disk regions. Abactinal granules crowded, often densely packed, sometimes obscuring plate surface. Highest density of granules on central region of disk.Granules and tubercles absent on New Caledonia specimen, present on Indian Ocean specimens. Pedicellariae, sugar-tong-like, three or four prominent teeth on valves, uncommon on abactinal surface, randomly distributed.Madreporite large, swollen, highly convex, surrounded by 12-18 abactinal plates.

Arm plates convex, three to five times the size of disk plates, continuing along arm in multiple rows, two or three plates continue from base distally, attenuating to one row of abactinal plates near arm tip, the 15-18 distalmost abactinal plates.Some tubercles present on base of arm, but plate surface largely bare. Pedicellariae absent from arm plates.Peripheral granules 10-20 (typically 12-15), angular to rounded in cross-section becoming more angular, prominent on New Caledonia specimen, more rounded, polygonal on Indian Ocean specimens. Peripheral granules around arm plates smaller, 20-60 surround smaller to larger plates, respectively. Marginal plates, 50-65 (typically about 55-60) in each interradius. Marginal plates largest interradially, becoming smaller distally. Distalmost superomarginals, often four to eight plates from the terminal plate, abut at arm tip. Marginal plates angular in cross-section, forming distinct lateral edge.Tong-shaped pedicellariae, with three to five teeth, present on Indian Ocean specimens on superomarginal and inferomarginal plates on spine clusters. Spinelets form continuous periphery around each marginal plate.

Superomarginal plate shape quadrate, forming distinct dorsal border, forming convex to linear contact with abactinal disk surface. Prominent, sharp, conical spine or array of conical spinelets present on dorsolateral superomarginal plate surface, which is otherwise bare. Granules or other accessories absent. Spinelets present on three to eight middle interradial superomarginal plates. Spines present or absent from these plates, but when present, in conjunction with 5-10 sharp spinelets. Superomarginal spines also absent on distalmost 10-15 plates from terminal, but present as continuous series on all other superomarginals.

Inferomarginals attenuate in size but at different rate from superomarginals, retaining a larger size relative to its superomarginal counterpart adjacent to arm tip. Clusters (7-25, usually approximately 15) of sharp, conical spinelets present on 16-25 middle interradial inferomarginal plates. Lowlying granules with points also present. Prominent spines similar to those on superomarginal spines, present on ventrolateral surface of inferomarginal plates occurring distally along arm, ending three to six plates from terminal. Aside from spinelets, inferomarginal plate surface bare. Terminal triangular approximately two to three times the size of adjacent superomarginal plates.

Actinal regions relatively small, in three or four irregular chevrons. Actinal plate extend to base of arms, rounded to polygonal in shape. Prominent, tong-like pedicellariae with three to five large teeth, nipple-like tubercles, sharp granular spinelets, and polygonal granules present on actinal plate surface, which is otherwise bare.Granular spinelets absent on New Caledonia specimen, present on Indian Ocean specimens. Actinal spinelets, 3-15 per plate, vary in size, scattered across different plates. Tubercles uncommon, but with greatest abundance adjacent to inferomarginal plates. Peripheral accessories bead-like but becoming more spinelet-like in Indian Ocean specimens. Peripheral accessories/spinelets form incipient shallow, grooves.

Furrow spines 12-15, flattened, blade-like in linear to slightly convex order parallel to tube foot furrow. Discrete space separates furrow spines from large tong-like pedicellariae, with three to five large teeth on valves. Additional bare regions surround pedicellariae. Peripheral granules, 12-15 with tips rough to spinelet-like. Adambulacral plate covered by five to seven spinelets/rough-tipped granules.

Furrow spines on mouth plates, 18-25. Mouth plate surface covered with accessory granules identical to those on actinal plates. 12-15 granules present along mouth plate suture, with tips roughened, worn down in Indian Ocean specimens. One or two large pedicellariae present on mouth angle plates adjacent, behind mouth plate furrow spines.

Figures

FIG. 5. — A-C, Circeaster arandae n. sp. (MNHN EcAs 11727); A, abactinal surface; B, actinal surface; C, abactinal arm disk surface; D-F, Circeaster kristinae n. sp. (WAM Z20694); D, abactinal surface; E, abactinal arm-disk surface; F, actinal surface. Scale bars: A-E, 1.0 cm; F, 0.5 cm.