Lydiaster Koehler, 1909

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 : 923-926

Genus Lydiaster Koehler, 1909

Lydiaster Koehler, 1909: 91 . — Halpern 1970a: 265.

TYPE SPECIES. — Lydiaster johannae Koehler, 1909 .

DIAGNOSIS. — Monotypic, see species diagnosis below.

Lydiaster johannae Koehler, 1909 ( Fig. 2 A-D)

Lydiaster johannae Koehler, 1909: 91 , pls III, fig. 9, VII, figs 1, 2, VIII, fig. 1.

Circeaster johannae – Halpern 1970a: 265; 1970b: 173. — Clark 1993: 251.

MATERIAL EXAMINED. — Madagascar. 104°15.7’S, 43°01.5’E, 750-810 m, 29.XI.1973, 1 dry spec., R = 11.5 cm, r = 4.1 cm ( MNHN EcAs 11724).

DISTRIBUTION. — Previously recorded only from northern Indian Ocean (type locality), 6°31’N, 79°38’45’E, 733 m (401 fms). Occurrence extended south to Madagascar. 733- 810 m.

DIAGNOSIS. — R/r> 2.7. Abactinal arm plates similar in size to those on disk. Granules two to five, and paddle-like pedicellariae with sharp teeth present ( Fig.2B ) on disk and arm plates. Abactinal, marginal, actinal surface/peripheral granules, coarse, angular. Marginal plate surface covered with granular spinelets. Spinelets more abundant on inferomarginals than on superomarginals. Arms broad, elongate. Actinal plates with one or two of any of the following: enlarged tubercles, paddle-like pedicellariae with sharp teeth, spines with roughened tips. Actinal granules angular, coarse with roughened tips. Furrow spines six or seven, angular in cross-section. Enlarged subambulacral spine laterally adjacent to adambulacral paddle-shaped, pedicellariae with sharp teeth. Enlarged subambulacral granules two to five, polygonal in crosssection present abradial to pedicellariae, adjacent to actinal plate region.

APOMORPHY LIST. — Nodes 24 to 23: 1.3, plate surface convex; 1.4, granules present; 1.6, granules coarse, round; 1.7, granule density heavy on central disk; 1.9, accessories form plate periphery; 2.1, SM spinelets present; 2.2, IM spinelets present; 2.6, MP peripheral granules fine; 2.8, IM accessories densely packed; 2.9, MP interradial abundance high; 2.10, MP peripheral granules fine; 3.1, actinal spinelets present; 4.3, subambulacral accessories abundant; 6.1, arms elongate.

Nodes 23 to Lydiaster johannae : 2.7, SM accessories densely packed.

DESCRIPTION

Disk, large thickened. Interradial arc curved to linear. Arms triangular, upturned. Disk surface swollen, sunken interradially. Disk plates rounded to irregularly polygonal, mound-like, convex. Plate size largest along radial and abradial series, decreasing in size distally. Disk plates smallest adjacent to superomarginal-disk boundary. Arm plates with no significant difference in size compared to disk plates. Arm plates in three or four series, irregularly distributed along arm. Distinct plate series absent. Granules 1-12 in number, large and coarse, present on plate surface. Granules crowded at disk center (8-12 per plate), decreasing in number (one to two per plate) and becoming more widely scattered closer to the disk-superomarginal boundary. Granules, enlarged, tubercular in appearance. Where granules have been removed or abraded, shallow concavities present. Granules present on disk and arms absent distally, approximately three to five superomarginal plates away from terminal plate. Only one to six granules present on arm plates.Pedicellariae relatively large, three to six teeth per valve, scattered over abactinal plate surface; typically one per plate, more heavily concentrated centrally on disk. Plates lacking surface granulation or pedicellariae smooth. Peripheral granulation, 10-60, typically 20-35, in number, evenly distributed around dorsal plate border. Peripheral granules angular with roughened tips, becoming jagged laterally between inferomarginal and superomarginal series.

Madreporite polygonal, enlarged, swollen, with well-developed grooves. Flanked by eight or nine abactinal plates.

Marginal plates 50-65 in number, from arm tip to arm tip. Largest interradially, decreasing in size distally. Paddle-like pedicellariae with three to six pointed teeth per plate present on surfaces of both marginal plate series. Typically one per plate, found near plate periphery adjacent to actinal intermediate region, or adjacent superomarginal or inferomarginal plate. Marginal series bordered by 20-90 angular-quadrate granules, evenly spaced. Peripheral granules form complete periphery, forming offset double rows between plates, forming shallow grooves between them. Peripheral granules largest along lateral edge between superomarginal and inferomarginal series, becoming finer between superomarginal and inferomarginal series.Peripheral accessories similar in shape and number to those of surrounding superomarginals.

Superomarginals widest interradially, becoming narrower distally with angular to rounded edges. Border with abactinal disk region straight to curved border. Sharp, thorny, granulose spinelets, 20-80 in number, typically 50-66, uniformly cover superomarginal surface. Spinelets largest, sharpest along lateral edge, becoming rounder, more hemispherical on periphery of plate, adjacent to inferomarginals and abactinal disk surface. Spinelets/granules scattered, highest abundance interradially, decreasing distally toward arm tips. Superomarginals one to six plates away from terminals with zero to eight granules/spinelets.

Inferomarginal series forming lateral ledge below superomarginals. Inferomarginal surface with 0-90 crowded granulose spinelets, covering nearly all open space. Granules/spinelets most heavily cover dorsoventral and lateral surfaces but absent adjacent to superomarginal plates. Abundance of granules/ spinelets highest interradially, decreasing distally.Inferomarginals, three to six plates away from terminals, bare or nearly so. Inferomarginal contact with actinal intermediate region straight to concave.

Terminal plate enlarged, two to three times size of adjoining superomarginals; triangular in outline with angles, blunt.

Actinal regions large, with single actinal plate series extending nearly 75% of arm length. Actinal plates polygonal, forming six or seven irregular chevrons. Actinal series adjacent to adambulacral series large; plates hexagonal. Chevrons adjacent to inferomarginal series smaller, more irregular in shape. Actinal plates covered with 2-10 large, block-like, angular to hemispherical granules, many with tips roughened. Several plates with one to four, large, blunt spine-like tubercles, polygonal in cross-section with tip roughened to jagged. Shallow grooves present. Single paddle-like pedicellariae with three to six teeth per valve present on actinal plates, scattered over actinal surface. Granule/spinelets, pedicellariae, tubercles more crowded adjacent to inferomarginal plate series, becoming more evenly spaced adjacent towards mouth and adambulacral series. Actinal accessories crowded along arm plates. Tubercles and pedicellariae continue along plates, decreasing in abundance distally. Distalmost actinal arm plates covered only by two to eight hemispherical granules. Actinal plate bordered by 5-15 granules, evenly spaced, block-like, angular in cross-section, many with tips roughened.

Adambulacral plates pentagonal. Furrow spines, four to six in number, compressed, triangular to prismatic in cross-section, thickened, arranged in continuous linear series. Pedicellariae, large and paddle-like, on adambulacral plate abradial to furrow spines, adjacent to one or two enlarged subambulacral spines. Spines triangular to prismatic in cross-section, with tip roughened. Remainder of adambulacral plate covered by four to eight angular, blockish granules similar to those of actinal plate surface, and one or two spine-like tubercles identical to those on actinal plate surface. Peripheral granules, 8-10, similar to those on actinal plates.

Mouth plate furrow spines, 10-15, similar to those on adambulacral plates, triangular to polygonal/prismatic in cross section. Compressed, blunt with tips roughened. Spines on mouth plates enlarged, triangular in cross-section. Mouth plates covered with blockish-angular granules similar to those on actinal plates. 10-15 granules form edge adjacent to suture between mouth plates, remainder of plate covered by 15-20 enlarged blockish-angular granules with tips roughened.

Figures

FIG. 2. — A-D, Lydiaster johannae (MNHN EcAs 11724); A, abactinal surface; B, pedicellariae; C, abactinal arm surface; D, actinal surface; E, F, Floriaster maya (NMNH E38662); E, abactinal surface; F, actinal surface; G, H, Cladaster analogus (NMNH E38569); G, abactinal surface; H, actinal surface. Scale bars: A, C-E, G, 1.0 cm; B, F, H, 0.5 cm.