Circeaster sandrae, 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 : 938-940

Circeaster sandrae n. sp.

( Fig. 6 A-C)

HOLOTYPE. — Southwest Pacific Ocean. Banc Combe, 12°17’S, 177°28’W, 780-794 m, 18.V.1992, 1 dry spec., R = 14.0 cm, r = 3.6 cm ( MNHN EcAs 11730).

PARATYPES. — New Caledonia. 23°10’S, 166°49’E, 870-1000 m, 31.III.1994, 1 dry spec., R = 6.5 cm, r = 2.7 cm ( MNHN EcAs 11731). — 21°00’S, 160°50’E, 745 m, 22.X.1986, 1 dry spec., R = 7.4, r = 3.5 cm ( MNHN EcAs 11732). — 20°23’S, 166°20’E, 800 m, 17.II.1989, 1 dry spec., R = 7.6 cm, r = 3.0 cm ( MNHN EcAs 11733).

Marquesas Islands. Île Nuku Hiva, 8°50’S, 140°10’W, 705-794 m, 9.IX.1997, 1 dry spec., R = 13.0 cm, r = 4.4 cm (MNHN EcAs 11734).

Tonga. NWTongatapu, 20°58’S, 175°16’W, 869-880 m, 9. VI.2000, 1 dry spec., R = 9.3 cm, r = 4.0 cm ( MNHN EcAs 11734).

ETYMOLOGY. — This species is named for my colleague Sandra Brooke ( OIMB).

DISTRIBUTION. — South Pacific Ocean, Tonga, New Caledonia, Marquesas Islands. 705-1000 m.

DIAGNOSIS. — R /r = 3-4. Abactinal arm plates similar to disk plates in size, becoming gradually larger on arm. Arm plates only one to two times as large as disk plates. Granules round, low scattered over disk, arm base, disappearing near arm tip. Granules rounded, low, scattered over marginal plate surface. Subambulacral spine enlarged, laterally adjacent to pedicellariae, paddle-like, toothed.

APOMORPHY LIST. — Nodes 20 to 19: 2.3, SM abutted over midline; 2.9, MP abundance, moderate; 3.2, actinal accessories, spiny. Node 19 to Circeaster sandrae n. sp.: 1.2, arm-disk plate transition, gradual; 4.2, subambulacral spine adjacent to pedicellariae.

DESCRIPTION

Disk moderately thick. Arms triangular. Interradial arcs linear.Abactinal plates round to polygonal, little

variation in shape, size.Plates on disk edge adjacent to superomarginals slightly smaller than those centrally on disk. Abactinal plates convex, appearing flatter in smaller specimen ( R = 6.5 cm). Pedicellariae paddle-shaped bearing three or four teeth uncommon on abactinal plates. Pedicellariae moderately large (about the size of two or three granules). Granules scattered, 1-30 per plate. Most granules (c. 20-30) central on disk, decreasing in abundance adjacent to superomarginals (approximately one to five). Peripheral granules, 10-40 (mostly 20-30), evenly spaced. Peripheral granules polygonal to round.Shallow grooves present. Abactinal arm plates enlarged, approximately twice the size of some disk plates, but some similar in size to carinal disk plates, oval to polygonal in shape. two or three plate series at arm base, forming single series distally along arm. Granules on arm plates few to absent. Distalmost abactinal arm plates bare, convex. Madreporite pentagonal to hexagonal, slightly swollen, convex with rounded edges, flanked by five to eight abactinal plates.

Marginal plates, 35-55, usually about 45-50, per interradius from arm tip to arm tip. Marginal plates with rounded edges, quadrate in transverse cross-section, rounded dorsolateral/ventrolateral edges. Superomarginal and inferomarginal series slightly offset forming zig-zag boundary. Granules absent between superomarginal and inferomarginal plates.

Abutted superomarginals, zero to six. Disk-superomarginal plate contact weakly convex to straight. Interradial superomarginal plates longest, becoming wider/shorter, closer to arm tip. Granules abundant, 20-100 (usually 50-80) coarse scattered, present on superomarginal plate surface. Granules most abundant interradially, decreasing distally. Granules absent on distalmost superomarginal plates.

Inferomarginal plates with higher abundance of granules, 0-200 granules coarse, scattered. Number of granules highest on interradial plates, decreasing to none adjacent to the terminal plate. Pedicellariae paddle-shaped, small, close in size to adjacent granules. Pedicellariae rarely present (sometimes one per radii) on lateral to dorsolateral plate surfaces.

Actinal plates quadrate, polygonal to irregularly round. Surfaces flat to slightly convex. Plates form five to eight irregular chevrons. Actinal region limited to disk in smaller specimens ( R ≈ 8 cm) but extending along arm in larger specimens ( R > 10.0 cm). Chevrons adjacent to adambulacral plates distinct but becoming irregular closer to actinal interradial region/inferomarginal plate contact. Some plate surfaces bare, or covered with 5-25 coarse, hemispherical, nubbin-like granules, or large, paddle-shaped pedicellariae with three to six teeth on valve. Granule abundance higher adjacent to mouth and adambulacral regions, decreasing adjacent to contact with inferomarginal plates. Granule shape, abundance varies based on size and locality. New Caledonia specimens with slightly larger dense covering of actinal granules in larger specimen ( MNHN EcAs 11732), scattered few granules in smaller specimen. Tonga specimen granules with rough tips, more angular in cross-section. Marquesas and Loyalty Ridge specimens closely resemble New Caledonia form, with smaller/fewer actinal granules. Actinal plate periphery surrounded by 4-30 granules, varying in shape from round to angular/polygonal.

Furrow spines 5-15, usually 12-14, vary by size, locality, position along tube foot furrow. Furrow spines laterally flattened, angular to flattened ovallike in cross-section. Tonga specimen furrow spines with roughened tips, foliate. Marquesas specimen with relatively thicker, angular furrow spines. Adambulacral plate with one to two thickened (approximately two to four times the furrow spines) subambulacral spine. Spine tip morphology varies from fluted/roughened (in Tonga specimen) to smooth (in New Caledonia specimen).Intermediate variation exists in New Caledonia and other specimens. Enlarged paddle-like pedicellaria adjacent to subambulacral spine, with three to six interlocking teeth on each valve. Granules 3-10, hemispherical to angular cover remainder of adambulacral plates, otherwise bare. Granules slightly coarser than those on other actinal plates.

Oral region sunken relative to actinal surface. Mouth plates with 15-20 furrow spines along tube foot furrow.One to three large pedicellariae, similar to those on other adambulacral plates, present on mouth plates. Tip of mouth plates with enlarged oral spines consistent in morphology with those on furrow spines. Tonga SW Pacific specimens with spines, laterally flattened, foliate. New Caledonia, Marquesas specimens mouth, furrow spines, more angular, thickened. Mouth plates covered with 10-15 hemispherical to angular granules with tips rounded to fluted/roughened.Ten to 15 such granules flank either edge of suture on mouth plate. Other granules scattered, distributed over mouth plates. Mouth plates bare where accessories are absent.

Colour in life is a bright red-orange.

Figures

FIG. 6. — A-C, Circeaster sandrae n. sp. (MNHN EcAs 11730); A, actinal surface; B, abactinal surface; C, abactinal arm-disk surface; D-F, Circeaster pullus n. sp.(CASIZ 172875); D, abactinal surface; E, abactinal arm-disk surface; F, oral surface. Abbreviations: Ped, pedicellariae; Sub, subambulacral spine. Scale bars: A, F, 0.5 cm; B-E, 1.0 cm.