Paralophaster paucispinus Mah 2023, n. sp.

Paralophaster paucispinus n. sp.

FIGURE 23 A–F

Etymology

The species epithet paucispinus is Latin for “few or little spines” alluding to the relatively few spines on the abactinal paxillae and the furrow spines.

Diagnosis

Body form stellate with broad disk, triangular arms (R/r=2.0), interradial arcs weakly curved (Fig. 23A, E). Abactinal paxillae with two to four spinelets (Fig. 23B). Disk broad with interradial regions divided by lobate plates (Fig. 23A, C). Marginal plates, only one row discernable, 26–28 per interradius (13–14 per arm side) (Fig. 23, D, E). Each marginal paxillae with 4–10 blunt spinelets. Furrow spines two proximally then one distally, subambulacral spines, two, widely spaced, lacking serrated shaft (Fig 23F).

Comments

Paralophaster paucispinus n. sp. is distinguished from other Paralophaster species by presence of significantly few spinelets on abactinal and marginal paxillae, as well as for low numbers of furrow and subambulacral spines.

Paralophaster paucispinus is one of three Paralophaster species occurring at bathyal depths (3250–3285 m), including Paralophaster godfroyi (2450 m) and Paralophaster lorioli (4572 m).

Description

Body stellate (R/r=2.0), thick, arms short and triangular. Disk broad, interradial arcs straight or weakly curved (Fig. 23A, E).

Abactinal surface paxillate, each with 2 to 4 short spinelets (Fig. 23B). Spinelets with denticulate or roughened tips. Paxillar plates with round bases. Body surface covered by membranous skin. Interradial regions with well-developed skeletal dividers with transverse extensions all formed from extended, lobate plates dividing the arms into their respective radial regions. These plates with 2 to 5 paxillae, identical to others on the disk. These interradial lobate plates culminate on the primary ring centrally on the disk. Lobate plates without paxillae otherwise lacking further accessories or features. Madreporite, quadrate, weakly raised with well-developed sulci located in contact with lobate dividers, surrounded by approximately 3 to 5 paxillae.

Marginal plates 26–28 per interradius (13–14 per arm side), interradially extending onto actinal intermediate surface (Fig. 23C, D, E). Only one clear series of enlarged paxillae-shaped marginal plates observable between the terminal plate and the interradius on the disk. Marginal plates widely spaced, each separated by an interval equivalent to the length of one adambulacral plate. Each marginal plate base broad and thick, irregularly round in cross section, approximately twice the thickness of adjacent abactinal plates. Paxillar heads convex, brush-like, bearing 4 to 10 blunt spinelets. Terminal plate, round, surface convex.

Actinal intermediate area spineless and plateless, covered with membranous skin, identical to that on the abactinal surface (Fig. 23D, E).

Adambulacral plates covered over with membranous dermis. Furrow spines two then one distally along arm, unwebbed, pointing away from one another, each with smooth surface, tip pointed (Fig. 23F). Subambulacral spines one or two, smooth faces. Oral plates triangular, covered with dermis, each plate with 6 webbed furrow spines, totaling 12 per interradius. Oral plate surface with no spines.

Occurrence

Scotia Sea, 3250–3867 m.

Holotype. USNM 1660601, SE of South Orkney Islands, Scotia Sea, Southern Ocean, −62.15, −40.642, 3250– 3285 m. Coll. R/ V Eltanin USAP, 24 March 1964. 1 dry spec. R=2.6 r=1.3.