Circeaster helenae, 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 : 930-934

Circeaster helenae n. sp.

( Fig. 4A, B )

HOLOTYPE. — Western Australia. 145 nautical miles NW off Port Hedland , mud, 18°37’S, 116°14.6’E to 18°38’ S, 116°44’ E, 696-700 m, 6.IV.1982, 1 dry spec., R ≈ 10-11 cm (arms broken, tips missing), r = 3.9 cm ( WAM Z20671).

ETYMOLOGY. — This species is named for Dr Helen Rotman-Clark, National Institute of Water and Atmospheric Research, in honour of her many contributions to asteroid taxonomy.

DISTRIBUTION. — Western Australia, Timor Sea/Indian Ocean. 696- 700 m.

DIAGNOSIS. — R/r ≥ 2.5. Granules largely absent from abactinal surface. Superomarginal plates abutted at midline. Superomarginals widest at arm base. Spinelets cover marginals, actinal plate surfaces. Spinelets cover dorsolateral, lateral, ventrolateral marginal plate, actinal surface. Subambulacral spine absent.

APOMORPHY LIST. — Nodes 15 to Circeaster helenae n. sp.: 2.3, SM abutted over midline; 2.9, MP abundance, moderate; 7.1, bivalve pedicellariae present.

DESCRIPTION

Disk thick, broad. Arms thick, wide. Abactinal disk plates form stellate region.Abactinal plates round to polygonal. Plates larger, oblong along radial regions becoming smaller, rounder interradially. Abactinal plates flattened to convex. Hemispherical granules few, scattered across surface, approximately one to four per plate, highest density around madreporite. Some plates with tiny paddle-like pedicellariae bearing approximately four to six teeth. Peripheral granules, 15-40, rounded, forming complete, evenly spaced border, forming shallow grooves between plates. One interadii with sublethal damage or congenital defect with approximately seven superomarginal plates present between abactinal interradial plates, similar in appearance to those described below. Madreporite polygonal, large, flanked by seven to nine granule covered plates.

Marginal plates, 30-50 arm tip to arm tip (arm tips are missing in the available specimen).Marginal plates wide, quadrate to diamond-shaped in lateral cross-section, edges rounded, peripheral granules, 100-150, distributed evenly around border of marginal plates. Both marginal plate series with spinelets or granules with spiny tips. Marginal plates. Shallow grooves present between marginal plates. Peripheral accessories around ventral inferomarginal surface with spinelets.

Superomarginals largest at arm base where plates abut at midline. Superomarginals offset, forming jagged contact boundary. Interradial plates are approximately 40-50% smaller than those at arm base. Superomarginals decrease in size distally along arm. Spinelets, 10-40 per superomarginal plate, highest abundance interradially, decreasing distally.Spinelets present dorsolaterally, absent from region adjacent to contact boundary between superomarginal and abactinal disk and region adjacent to boundary with inferomarginal plates along lateral surfaces on all plates. Superomarginal dorsal surface bare.

Region on inferomarginals adjacent to superomarginal contact bare. Some flattened to hemispherical granules on lateral inferomarginal surface. Remaining inferomarginal surface with 50-100 sharp, conical spinelets and/or spiny tipped granules, covering ventral, ventrolateral surface. Spinelets evenly distributed; greatest abundance on ventral inferomarginal plate surface. Arm tips, terminal plates unknown.

Actinal surface with six or seven chevrons, these irregular interradially, adjacent to inferomarginals. Chevron plates polygonal to rounded, those in series adjacent to adambulacral furrow with largest-sized plates, pentagonal-hexagonal in shape. Consecutive chevron plates elongate, polygonal, becoming more irregular in shape interradially adjacent to inferomarginals. Actinal surface covered with three to eight short, sharp spinelets similar to those on ventral inferomarginal surface and/or 15-30 pointed-rounded granules. Spinelets, when present, occur centrally on plate with granules or other accessories absent between spinelets. Granules dense, evenly distributed. Large bivalve pedicellariae with thin, flat valves, with 10-15 low serrations across edge, scattered across actinal surface. Largest chevron adjacent to adambulacrals with prominent large spinelets, approximately three to six enlarged pedicellariae on each plate, surrounded by 20-30 accessory granules/spinelets.Actinal plate periphery 20-40 granules similar to those elsewhere on body, forming evenly spaced border, shallow grooves between actinal plates.

Furrow spines, six to eight, flattened, chiselshaped, arranged in weakly curved to straight series. Discrete bare region present between furrow spines and enlarged pedicellariae on adambulacral plate. Adambulacral pedicellariae composed of either one enlarged, curved pedicellaria or two paddle-shaped pedicellariae closely adjacent to one another. Serration on valves low to absent on single, enlarged valves, but smaller paddle-shaped pedicellariae with seven or eight prominent teeth on each valve. A second space sets off the pedicellaria from remaining accessories on the adambulacral plate.Adambulacral plate surface covered by approximately three to five (usually four) large, tapering spinelets, followed by 6-10 short, granular spinelets identical in size, shape to those on actinal surface.

Furrow spines on mouth plates, approximately 10-12, with enlarged blunt, round spines directed into mouth. Spines flattened, triagonal to polygonal in cross-section. Enlarged curved pedicellariae similar to others on adambulacral plate present behind furrow spines, discrete space on adambulacral plate. Approximately 18-25 enlarged granules, spiny-angular flanking suture on mouth plates. Suture deep. Approximately 20-35 granules covering adambulacral surface.

Circeaster magdalenae Koehler, 1909 ( Fig. 4 C-E)

Circeaster magdalenae Koehler, 1909: 88 , pl. V, figs 1-3, VI, fig. 2.

MATERIAL EXAMINED. — Madagascar. 13°50.0’S, 47°37.0’E, 850-1125 m, 27.II.1975, 1 dry spec., R = 11.6 cm, r = 5.2 cm ( MNHN EcAs 11725).

DISTRIBUTION. — Previously recorded only from 15°11’N, 72°28’45’E, 1668-1703 m (912-931 fms). Occurrence extended to Madagascar. 850-1703 m.

APOMORPHY LIST. — Nodes 16 to 15: 7.3, elongate pedicellariae present; 7.4, sunken pedicellariae present.

Nodes 15 to C. magdalenae : 1.6, granules coarse, round.

DIAGNOSIS. — R/r = 2.2. Transition abrupt, between disk and arm plates with bare abactinal arm plates. Pedicellariae elongate with enlarged jagged teeth, sunken into body surface on actinal surface, adambulacral plates. Spinelets cover dorsolateral, lateral, ventrolateral marginal plates, actinal surface. Circeaster with thick, broad arms. Subambulacral spine absent.

DESCRIPTION

Disk, thick, large. Arms broad at base. Abactinal plates rounded to irregularly polygonal. Plate surface convex, low, mound-like. Abactinal plates, larger at center of disk, decreasing in size, but not greatly so, adjacent to contact with superomarginal plates, adjacent to the base of the abactinal arm plates. Carinal and primary circlet plate series not clearly distinguished.Granules,zero to six in number present on each abactinal plate; coarse, low hemispherical, crowded. Granule abundance heaviest at disk center (five or six per plate), decreasing (one or two per plate) distally adjacent to superomarginals. Granule size increases as granule number decreases.Individual granules can occupy nearly entire abactinal plate surface. Granular-shaped spinelets, one to three in number, also present on disk periphery. Small paddle-like pedicellariae, similar in size to smaller granules with three to five teeth on each valve, rare on abactinal surface (only one or two present on specimen). Disk plates adjacent to superomarginals, largely bare of granules. Arm plates smooth, bare, enlarged three to six times the size of abactinal disk plates, directly abutting forming a mosaic distinctly separated from disk plates ( Fig. 4D ), few granules present. Abactinal arm plates largest at arm base, decreasing in size until adjacent to terminal plate, extending to arm tip. Plates hexagonal, becoming more irregularly polygonal to rounded distally. Peripheral granules, 8-60, usually 25-35, forming complete borders around all abactinal plates. Granules form crowded borders around disk plates, evenly spaced around arm plates.

Madreporite polygonal, convex, grooves poorly developed, flanked by eight abactinal plates.

Marginal plates 60-75 (from arm tip to arm tip); widest, largest, interradially becoming smaller, more elongate distally. Superomarginal and inferomarginal series correspond one to one interradially. Superomarginal and inferomarginal series offset, becoming more jagged distally.

Superomarginal corners angular to rounded. Superomarginal dorsolateral border rounded to flattened. Superomarginals forming enlarged, irregular jagged to polygonal contacts intruding onto arm region adjacent to bare arm plates. Bare superomarginal surface identical to abactinal arm disk surface. Sharp, thorny spinelets, 1-35 in number per plate, widely scattered, on dorsolateral, lateral surfaces.Spinelets absent from disk surface adjacent to abactinal disk plates but covering dorsal surface of superomarginal plates on arm plates adjacent to arm disk plates. Spinelets/granules most abundant interradially, decreasing distally. Spinelets adjacent to terminal plate, hemispherical, rounded. Peripheral granules, 20-90, bead-like, becoming more pointed, spine-like along lateral edge adjacent to inferomarginal plates.

Inferomarginal series, slightly extended, forming narrow border, especially along arms.Inferomarginal plates wide, forming prominent ventral border. In cross-section, ventrolateral border rounded contact border with actinal intermediate plates, convex. Ventrolateral surface with 2-100 granule-likespinelets, highest interradially, decreasing distally, arm becoming bare or nearly so one to five plates away from terminal.Spinelets more spine-like interradially, more granule-like distally, scattered widely over plate surface. Spinelets most abundant covering ventral, ventrolateral, lateral plate surfaces, becoming bare laterally, adjacent to superomarginal contact.Inferomarginals adjacent to terminal, short, tiny granular spinelets/granules, 30-150 forming complete bor- der. Total number of peripheral granules decreases distally. Peripheral accessories more spinelet-like interradially, becoming more granule-like distally, adjacent to the terminal plate. Inferomarginals rarely with one or two bivalve pedicellariae, three to six sharp teeth on each valve.

Terminal plate triangular, smooth, approximately size of adjoining superomarginal plate.

Actinal regions large, extending from disk along approximately 75% of arm distance. Actinal plates in six to eight irregular chevrons, becoming less ordered, more irregular away from the ambulacral furrows, toward interradial arcs, inferomarginals. Plates in chevron adjacent to adambulacral plates largest, quadrate in shape. Actinal plates covered by 6-40 sharp conical spinelets, crowded but evenly spaced. Size largely homogeneous, but spinelets on actinal arm plates are two to three times larger. Spinelets not forming distinct border but forming nearly continuous cover up to contact with inferomarginals, forming shallow channel between actinal, inferomarginal plate series.

Spinelet cover nearly complete save for 20-30 unusual bivalve pedicellariae, inset into, flush with actinal surface. Pedicellariae shape variable:straight, boomerang-like, T-shaped to sinusoidal, large (may be present over one actinal) valves with 4-20 sharp, interlocking teeth.

Pedicellariae separated from other actinal spinelets by discrete furrows bordered by 14-18 enlarged spines on either side.No clear pattern of pedicellariae distribution evident, but higher numbers appear to be present along actinal arm adjacent to mouth plate regions in single specimen examined

Furrow spines, 8-10, compressed, narrow, triagonal to polygonal in cross-section, identical in size. Adambulacral plate quadrate to polygonal, decreasing in size distally. Large pedicellariae, similar to that on the actinal plates, separated by a large gaps separating pedicellariae from furrow spines, other actinal spinelets on adambulacral plate. Furrow pedicellariae transverse to plate length, parallel to furrow spines, valves with 4-20 interlocking teeth. Pedicellariae straight to irregularly curved, few extending onto adambulacral plate adjacent to actinal intermediate region. Pedicellariae becoming smaller distally, shifting from single to two pedicellariae at approximately 30-40 adambulacral plates from terminal. Adambulacral plate covered by 30- 50 short, sharp spinelets, largely homogeneous in size, occur with three to six larger spines, two to three times the size of other spinelets, increasing in size and abundance distally. Plates adjacent to mouth plate or closer to mouth region with largely homogenous spinelets, increasing to one to three enlarged spines, approximately five or six plates away from mouth plates.

Furrow spines on mouth plates 12-15; enlarged, thickened, angular to polygonal in cross-section. Enlarged mouth plates directed into mouth; thickened, polygonal in cross-section. Furrow spines separated from mouth plate accessories by discrete furrow. Pedicellariae absent from mouth plates. Mouth plates covered by 30-50 blunt, curved, sometimes conical spines with smooth to jagged tips. Eleven to 12 enlarged spine-like granules form border to suture along each side of mouth plate. Other spines/spinelets on mouth plates similar to those on actinal plate surface.

Figures

FIG. 4. — A, B, Circeaster helenae n. sp. (WAM Z20671); A, abactinal surface;B, actinal surface; C-E, Circeaster magdalenae Koehler, 1909 (MNHN EcAs 11725); C, abactinal surface; D, close-up of arm; E, actinal surface. Abbreviation: P, pedicellariae. Scale bars: A, C, 2.0 cm; B, D, 1.0 cm; E, 0.5 cm.