Astroceramus kintana, Mah, 2018

Mah, Christopher L., 2018, New genera, species and occurrence records of Goniasteridae (Asteroidea; Echinodermata) from the Indian Ocean, Zootaxa 4539 (1), pp. 1-116 : 15-17

Astroceramus kintana n. sp.

Figure 4 A–F

Etymology. The species epithet kintana is the Malagasy word for “star” alluding to this species strongly stellate shape. Noun is held in apposition.

Diagnosis. This species is distinguished by the presence of elongate abactinal plates along approximately 50% of the arm distance by abutted superomarginal plates ( Fig. 4A ). It possesses seven or eight furrow spines and two enlarged subambulacral spines ( Fig. 4F ).

Comments. This species and Astroceramus eleaumei n. sp. share several characters, including the presence of abactinal plates extending well along the arm as well as elongate arm length and an overall strongly stellate body shape; the two species are found in close geographic proximity and are similar to one another in appearance.

Occurrence. Northeast of Glorioso Island, west of Mayotte Island, 455–614 m

Description. Body stout, strongly stellate (R/r=2.2–3.2) with elongate, tapering arms, triangular in shape. Interradial arcs broad, weakly curved to straight ( Fig. 4A, D ).

Abactinal plates abutted forming flush pavement, each plate hexagonal to polygonal or round in outline except for those on arm. Abactinal surface continues onto approximately 50% of proximal arm distance. Individual arm plates elongate, variably triangular to irregular in shape.

Abactinal plates mostly homogeneous in shape, size becoming more irregular distally adjacent to superomarginal contact. Abactinal plates largely bare and smooth save for coarse, round small tubercular granules, zero to five, mostly one to three present on the center of each plate ( Fig. 4B ). These granulated plates present mainly on interradial regions but can occur on arm plates. Plates with widely spaced, coarse peripheral granules, 10–30, mostly 15–25. Paddle-shaped pedicellariae with four to seven widely spaced teeth on each valve, present on a minority of abactinal plates, ( Fig. 4B ) mostly present interradially adjacent to the superomarginal contact, present either individually or with one or two granules present. Pedicellariae sit within a pit extending into the surface of the plate. Other than granules and pedicellariae, plate surface is bare and smooth. Abactinal plates possess numerous crystalline nodules, 10–120, mostly 30–100, widely spaced and inset into the surface of each plate ( Fig. 4B ). These are numerous proximally on the disk but begin to pinch out on plates distally adjacent to the superomarginal contact and along arm plates. Madreporite quadrate, flanked by four plates. Papulae present primarily along radial regions, six per plate, present at each plate angle.

Marginal plates 36–38 per interradius (arm tip to arm tip), with superomarginals abutted over midline along each arm. Superomarginals offset forming zigzag contact along distal 50% of arm distance. Marginal plates quadrate in outline interradially becoming wider along the arm base and becoming more elongate distally. Distalmost superomarginals, 10–11, abutted over midline with a more prominent abactinal superomarginal facing along arm tip. Superomarginal surface covered by coarse, closely spaced, abundant granules ( Fig. 4C ), approximately 20–100 on dorsolateral surface with 20–60 widely present on abactinal superomarginal plate surface. Lateral surface with few to no granules. Granules present in greatest numbers interradially decreasing significantly along distal superomarginals along arm. Peripheral granules round, coarse, approximately 20 per side/ roughly 80–150 around the complete plate. Pedicellariae paddle-like, one to three present on interradial superomarginal plates, decreasing to none along arm. Superomarginal with zigzag like contact with offset plates proximally becoming more 1:1 near arm tip. Inferomarginal plate actinal surface covered by 20–100 close but widely distributed, coarse granules, including a second peripheral series of granules, approximately 20 per side, about 80–100 in total, set within the peripheral inferomarginal granules. Terminal plate triangular in shape, smooth surface.

Actinal surface composed of approximately six to eight full series in chevron formation ( Fig. 4D ) with the remainder irregularly present distally adjacent to interradial inferomarginal contact. Actinal plates range from quadrate to irregularly round in shape with larger plates present proximally becoming smaller and more irregular distally. Actinal plates adjacent to adambulacral plates rectangular and in addition to granular cover, nearly every plate with mostly one, but exceptionally two or more, paddle-shaped pedicellariae ( Fig. 4E ) identical to those present on the abactinal surface, set into s pit on each plate. Pedicellariae absent from most other actinal plates but a minority of them, one to five do have pedicellariae. Actinal plate surface covered by five to 20, mostly 10–15 widely spaced coarse round to pointed granules ( Fig. 4D, E ). Peripheral granules number approximately seven per side, approximately four to 40 total, most showing approximately 25–30 total.

Furrow spines seven or eight blunt tipped, round in cross-section in straight to weakly palmate series. Subambulacral spines two, both thickened, bullet shaped, blunt tipped, set off from furrow spines by discrete space ( Fig. 4F ). On proximal plates the proximal-facing subambulacral spine is generally half the size of the distal-facing subambulacral spine. This latter large subambulacral spine is easily the width of three furrow spines with a large bulbous round tip. A minority of adambulacral plates with tong-like pedicellariae between the enlarged subambulacrals and the smaller, angular granules present. Remainder of adambulacral plate surface with four to 12 angular granules, widely spaced on plate surface. Oral plate furrow spines, eight to 10, quadrate in cross section with rounded edges, on oral plate, with one enlarged blunt spine per paired plate, triangular in cross-section projecting into mouth. Oral plate Subambulacral spines four, quadrate in cross-section, blunt-tipped with round to angular edges, set off from furrow spines by a discrete space. Paired, large angular granules, eight, present on tissue covered contact between oral plates. Approximately eight to 10 angular granules, widely spaced, present on remainder of oral plate.

Color in life: orange.

Notes on juvenile specimen. One specimen (MNHN IE-2013-17272) with R=1.2 shows only five superomarginals abutted over the midline but with approximately seven abactinal plates extending from the disk onto the arms. Ten superomarginals present per interradius. Actinal plates were strongly convex. Furrow spines three or four.

Material Examined. Holotype : IE-2013-17176 . Off west coast of Mayotte Island, 12° 47 'S, 44° 58' E to 12° 46 'S, 44° 59' E, 455–460 m. Coll. DW 4844 , Jan 30, 2017. 1 wet spec. R=7.7 r=2.4. Paratypes: IE-2013-17170 , Northeast of Glorioso Island , 11° 30'S, 47° 29' E to 11° 29 'S, 47° 29' E, 614– 583 m. Coll . DW 4813 , 25 Jan 2017. 1 wet spec. R=6.2 r=2.7 , IE-2013-17174 Northwest of Mayotte Island, 12° 30'S, 44° 55' E, 606– 610 m. Coll . DW 4863 Feb. 6 2017. 1 wet spec. R=6.8 r=2.7 , IE-2013-17182 , Off the southeast coast of Mayotte Island, 12° 56'S, 45° 15' E, 474–505m, Coll. S. Samadi , DW 4865 , Feb 7, 2017. 2 wet specs R=6.4 r=2.2, R=7.7 r=2.9 .

IE-2013-17272 , Northeast of Glorioso Island , 11° 30'S, 47° 28' E, 219– 224 m. Coll . DW 4808 , Jan 25, 2017 . R=1.2 r=0.5

Figures

FIGURE 4. Astroceramus kintana n. sp. Holotype IE-2013-17176. R=7.7 r=2.4 cm. A. Abactinal surface. Scale bar=2.0 cm. B. Closeup of abactinal plates showing crystalline nodules and pedicellariae. Scale Bar=0.1 cm. C. Closeup of superomarginal plate surface. Scale Bar=0.1 cm. D. Actinal surface. Scale bar=2.0. E. Closeup of actinal surface showing granules and pedicellariae. Scale bar=0.1 cm. F. Closeup of furrow spines, adambulacral accessories. Scale Bar=0.2 cm.