Circeaster loisetteae, 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 : 927-930

Circeaster loisetteae n. sp.

( Fig. 3 )

HOLOTYPE. — Western Australia. NW of Tork Sound , soft bottom, 12°54.4’S, 123°0.2’E to 12°50.6’S, 123°0.4’E, 452-462 m, 15.II.1984, 1 dry spec., R ≈ 12.0 cm (arm broken), r = 4.6 cm ( WAM Z20670).

PARATYPES. — Western Australia. NW of Beagle Bay, Western Australia, soft bottom, 15°08.6’S, 121°3.4’E to 15°6.0’S, 121°6.6’E, 500-504 m, 11.II.1984, 1 dry spec., R = 12.0 cm, r = 5.4 cm ( WAM Z20714). — NW of Collier Bay, WA soft bottom, 13°50.3’S, 122°18.5’E to 13°53.4’S, 122°16.7’E, 452- 450 m, 13.II.1984, 1 dry spec., R = 12.4 cm, r = 4.2 cm ( WAM Z20715). — WNW of Lacepede Archipelago, Western Australia on soft bottom, 15°40.2’S, 120°37.3’E to 15°42.6’S, 120°34.6’E, 500-504 m, 10.II.1984, 3 dry specs, R = 12.7 cm, r = 4.5 cm, R = 11.3 cm, r = 4.1 cm, R = 12.0 cm, r = 4.7 cm ( WAM Z20716).

Solomon Islands. 9°6.9’S, 159°53.2’E, 896-912 m, 25.IX.2001, 1 dry spec., R = 16.1 cm, r = 4.5 cm ( MNHN EcAs 11726).

ETYMOLOGY. — This species is named for Loisette Marsh, retired curator of Echinoderms at the Western Australian Museum and collector of many of the specimens examined herein.

DISTRIBUTION. — Western Australia/Timor Sea, Solomon Islands. 452- 912 m.

DIAGNOSIS. — R /r ≥ approximately 3.0. Abactinal arm plates not enlarged relative to disk plates in specimens with R ≈ 12.0 cm ( Fig. 3B ), but present at R = 16.0 cm ( Fig. 3D ). Abactinal granules up to three if present, sparingly distributed over disk center. Circeaster with superomarginals abutted at midline. Marginal plate series with granular spinelets, these are more abundant on inferomarginal plates (ventral surface). Actinal surface covered by spinelets, spine-tipped granules. Pedicellariae paddle-shaped. Subambulacral spine absent.

APOMORPHY LIST. — Nodes 16 to 14: 1.5, granules, when present; 1.7, granules distributed heavily on disk center to completely absent; 2.10, MP peripheral spinelets present.

Nodes 14 to Circeaster loisetteae n. sp.: 2.3, SM abutted at midline.

DESCRIPTION

Disk thick. Arms elongate ( R /r ≈ 3.0 to ≈ 5.0), tapering. Tips upturned. Interadial arcs rounded. Abactinal plates polygonal to rounded, mound-like, slightly tumid to flat, similar in size, but smaller, more numerous interradially. Disk plates relatively small (c. 10-12 across arm base). Abactinal plates largely limited to disk in specimens under R ≈ 12.0 cm forming acute triangular regions adjacent to proximal superomarginals abutted at midline. Abactinal arm plates, few, bare, two to three times the size of those on disk, present on arm in specimen with R = 16.0 cm, occurring irregularly between superomarginals, abutted on abactinal surface. Arm plate arrangement varies from arm to arm. Grooves present over radial regions, becoming shallower interradially.Granules sparingly present (zero to three per plate) but largely absent. Occurrence of granules increases adjacent to madeporite. Peripheral border composed of 12-50 (typically 20-35) coarse, evenly spaced, angular to rounded granules. Paddle-like pedicellariae, about one fifth the size of the plate, with wide,serrated valves,distributed along radial and abradial plates,largely absent from interradial regions. Madreporite hexagonal to polygonal flanked by five or six polygonal plates in the smaller specimens ( R ≈ 12.0 cm), 10-12 plates in the largest specimen.

Marginal plates numerous, 60-70 per interradius (arm tip to arm tip), angular in cross-section, forming distinct dorsolateral edge. Marginal plates surrounded by c. 60-120 angular-rounded granules decreasing distally.Terminal plate rounded, enlarged (approximately equivalent in size to the adjacent terminal superomarginals).

Superomarginals abutting at midradius for over 50% of the arm length. Abactinal plates irregularly present between abutting superomarginals, resulting in angular or polygonal contact boundaries between superomarginal and abactinal disk plates. Contact boundary between superomarginal and disk plates curved to straight, plates with angular to rounded corners.Superomarginal plates narrow.Sharp spinelets, 2-20 in number, scattered, most abundant interradially (c. 18) decreasing distally on dorsolateral edge of each superomarginal plate, becoming absent from distalmost superomarginal plate adjacent to tip (approximately12-15 away from terminal plate).Superomarginal plate surfaces otherwise lacking accessories on both dorsal side adjacent to disk plates, lateral side, adjacent to inferomarginal plate contact.

Inferomarginals rounded-angular in cross-section, forming discrete ventrolateral angle. Inferomarginal surface convex. Lateral surface of inferomarginal plate adjacent to superomarginals bare. Sharp, conical, evenly spaced spinelets, approximately 2-70 (typically about 60) in number, covering all but bare inferomarginal surface adjacent to the superomarginals. Spinelets adjacent to actinal region largest, most prominent.

Actinal region large, composed of approximately six to nine irregular chevrons. Shallow grooves present. Actinal plates limited to disk, with a small series of single plates extended to base of arm. Chevrons adjacent to furrow plate series most ordered, becoming smaller, more jumbled approaching contact boundary with inferomarginal series. Actinal plates more elongate, quadrate in shape proximal to tube foot furrow, becoming more irregularly polygonal at contact boundary with inferomarginal plates. Actinal plates covered by 4-50 coarse, crowded granules. One to eight, typically one to four, sharp, pointed spinelets present on center of nearly every actinal plate. Spinelets stand two to three times over low-rounded granules. Actinal accessories evenly scattered on plate surface. Spinelet abundance higher on plates adjacent to inferomarginal-actinal plate contact boundary. Periphery of each plate surrounded by 15-50 (usually about 20-30) sharp spinelets, forming close border.

Actinal pedicellariae variably present. When present, one or two pedicellariae present on all adambulacral plates and actinal plates adjacent to adambulacrals. Abundance becoming irregular to absent adjacent to the inferomarginal plate series. Paddle-like pedicellariae present, with serrated valves. Three to seven teeth present on each valve. Pedicellariae positioned on proximal edge of adambulacral. In MNHN EcAs 11726 (from the Solomon Islands) pedicellariae largely absent from intermediate actinal region.

Five to 10 (usually seven to eight) thickened furrow spines, polygonal to quadrate in cross-section with roughened tips. Furrow series straight to curved. Bare region between furrow spines, adambulacral accessories. A single large, paddle-shaped pedicellaria with five to seven prominent teeth sits immediately behind furrow spines, either in bare region or more centrally on adambulacral plate; pedicellariae otherwise absent. One to six sharp spinelets present on adambulacrals, actinal plates additionally covered by 30-40 crowded pointed to round granules. Twenty to 30 spiny to rounded, well-spaced granules forming peripheral border around each plate.

Furrow spines on mouth plates, 8-15, polygonal to quadrate in cross section on mouth plates. Paired, enlarged, thick, triangular in cross-section, with smooth surface at tip of mouth plate. Oral plates covered with 70-80 heterogeneous granules, most with tips, roughened or spiny. Subambulacral spines enlarged, quadrate to polygonal in cross-section. Larger subambulacral spines with clavate tips. Two sets of enlarged granules, 10-15 with rough tips form incomplete to complete edge along groove present between mouth plates.

Figures

FIG. 3. — Circeaster loisetteae n. sp.: A-C, WAM 20716; A, abactinal surface showing absence of enlarged arm plates; B, abactinal surface of arm showing enlarged arm plates;C, actinal surface;D, MNHN EcAs 11726,Solomon Islands,abactinal arm surface showing etching/notches on marginal plates from possible predation (see Discussion). Scale bars: A, B, D, 1.0 cm; C, 0.5 cm.