Cladaster katafractarius, 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 : 31-32

Cladaster katafractarius n. sp.

Figure 10 A–D

Etymology. The species name katafractarius is Latin for “armored solider” alluding to the large number of abutted superomarginals (i.e. armor) and numerous pedicellariae on this species.

Diagnosis. A species distinguished by arms elongate, five or six superomarginal plates abutted ( Fig. 10A ) along each arm (R=3.2), bivalve pedicellariae on actinal plates ( Fig. 10D ), and four furrow spines.

Comments. This species invites comparison with Cladaster macrobrachius H.L. Clark 1923 and Cladaster rudis Verrill 1899 , from South Africa and the tropical Atlantic, respectively. Both of these species show more than a single pair of abutted superomarginal plates present on the arm ( Fig. 10A ). The Atlantic Cladaster rudis apparently shows only the distalmost three to four superomarginals abutted over the arm ( Clark and Downey 1992: 240) which differs from Cladaster katafractarius n. sp. which in turn displays five or six abutted superomarginals. Superomarginals on the arms of Cladaster katafractarius n. sp. are also wider than those on Cladaster rudis .

Cladaster katafractarius n. sp. shares several characters in common with Cladaster macrobrachius . Both species have relatively elongate arms with more than three abutted superomarginal plates extending along the arm. Shape of the abutted superomarginals is also similar between the two species. Several characters also differ between the two species. Cladaster macrobrachius possesses largely three furrow spines whereas Cladaster katafractarius n. sp. possesses largely four spines. Abactinal surface pedicellariae morphology between the two species is also different with Cladaster macrobrachius displaying round, paddle-like pedicellariae whereas Cladaster katafractarius n. sp. displays wide, bivalve pedicellariae ( Fig. 10D ).

Occurrence. New Caledonia, Western Indian Ocean , 530–807 m.

Description. Body stellate (R/r=2.0–3.1), arms triangular, interradial arcs weakly curved to straight. Holotype with one arm lost ( Fig. 10A ).

Abactinal surface flattened, composed of abutted abactinal plates, round to polygonal in outline, individual plates weakly to strongly convex ( Fig. 10B ) forming continuous pavement with shallow grooves between convexities. Abactinal plates present primarily on disk and at arm base as superomarginals abut along arm midline ( Fig. 10B ). Most abactinal plates homogeneous in size and shape with relatively few showing excessively larger or smaller sizes. Plates covered by coarse, spherical to bullet-shaped, deciduous granules which leave a distinct shallow, concavity on the plate surface. Abactinal plate central surface show eight to 20 convexities per plate. Peripheral granules, 10–50, more bullet-shaped forming single, widely spaced series around each plate, apparently more tenacious than those on central surface which have mostly been lost. Approximately three granules occur along a 1.0 mm line. Other than coarse granules, abactinal plate surfaces are bare and smooth. Paddle-shaped pedicellariae with round clam-shaped valves (about 1.0– 1.5 mm in width) present on a minority of abactinal plates, with only a single pedicellaria present per plate. Pedicellariae occur in a shallow pit on each plate when present. Papulae six present around edges of plates along radial regions. Madreporite trapezoidal in shape, flanked by four abactinal plates. Abactinal surface appears sunken below the plane of the superomarginal plates where they are in contact.

Superomarginal, inferomarginal plates 18 per complete interradius (arm tip to arm tip) at R= 3.2 cm to 30 per interradius at R= 6.5 cm. Marginal plates mostly with 1:1 correspondence interradially but becoming offset with a more zigzag contact between them distally. Superomarginals with distinct abactinal facing, forming approximately (0.4/1.6) 25% of the total ‘r’ distance from disk center to edge of interradius. Superomarginals rectangular, elongate in outline, broader interradially becoming narrower distally along arm as they abut along midline distally ( Figs. 18A, B ). In the larger New Caledonia specimens the interradial regions are much thicker and with a welldeveloped lateral edge. Distalmost superomarginals abutted, six to ten pairs on distalmost arm region. The Indian Ocean holotype shows three of the arms with two abutted superomarginals in addition to one which is incomplete and with arm damage. All but one of the paratypes from New Caledonia also show arm damage, with only one specimen from IE-2013-6898 displaying five undamaged arms. Superomarginal plates with round, coarse granules, (approximately 20x30, width x length respectively, with approximately>100 total), essentially consistent in morphology with those on abactinal surface, in a widely spaced, single series forming the periphery around each plate. Superomarginal plate surface displaying shallow convexities where round, coarse, apparently deciduous widely spaced granules, approximately 50 to 200 covered the plate surface, both abactinal and lateral, but have since been abraded. More distalmost superomarginals adjacent to the terminal lacking granular pitting partially on abactinal surface. Inferomarginal plate surface covered with similar numbers of granules, up to 200 many of which are retained on the type. Peripheral granules similar in morphology and arrangement as those on the superomarginals. Shallow concave pitting as observed on the abactinal surface also present on the inferomarginal surface where granules have been abraded. Terminal plate triangular in shape, smooth surface. No pedicellariae observed on marginal plate surface.

Actinal surface composed of two full plate series, one irregular set in chevron formation ( Fig. 10C ). Actinal plates quadrate to irregularly polygonal in shape. Surface of each plate covered by round, coarse granules similar in morphology to those occurring on inferomarginals and elsewhere on body surface. Some central actinal intermediate plates with slightly larger, round granules than those elsewhere on the body surface. Actinal plate central surface with four to 15 widely spaced, round granules present. Peripheral granules, five to 30, widely spaced, slightly smaller than those on central surface. Full actinal series adjacent to the adambulacral series each with a prominent elongate, bivalve pedicellariae with broad valves, each about 1.0–2.0 mm wide sitting at perpendicular or tangential angles to tube foot groove ( Fig. 10D ). Valves wide, smooth. Most abundant proximally adjacent to mouth becoming less common distally adjacent to inferomarginals.

Furrow spines primarily four or five. Smaller individuals with some plates bearing only three spines irregularly interspersed along the adambulacral plate series. Furrow spines blunt, cylindrical in cross-section with central spines most elongate, widely spaced, forming complimentary, interdigitate series with furrow spines of opposite side. First 10 adambulacral plates all show an enlarged club-like subambulacral spine, at least twice as thick as a furrow spine ( Fig. 10D ), with a broad rounded tip, but 10% shorter than the highest furrow spine. Subambulacral spines one or two, with primarily one spine present proximally, increasing to two distally. Remaining subambulacral accessories composed of approximately four to six thick, round to pointed granules which are approximately 35% of the height of the subambulacral spine. Adambulacral plates with a single series of widely spaced single row of coarse granules, six to 20, variably round to teardrop shaped. Oral plate with four to six furrow spines, with one elongate, blunt, spine, triangular in cross-section pointed into the mouth (two total per interradius). Oral plate surface with two (one per plate) prominent, elongate blunt spines. Each oral plate with three shorter (25% of elongate oral plate spine) spines, each paired off against one another along the midline sulcus of the oral plate. Adambulacral plates quadrate to square in shape.

Material Examined. Holotype. IE-2013-17245 Western Indian Ocean. 11° 30 'S, 47° 30' E to 11° 30 'S, 47 °29' E, 694–733 m. Coll. BIOMAGLO. 25 Jan 2017. DW 4814 . 1 wet spec.c R=3.2 r=1.6.

Paratypes. IE-2013-6898 New Caledonia, 22°58’S 167°20’4”E, 530–535 m, Coll. Richer de Forges , 19 Sept 1986, VAUBAN dr. 18. 2 dry specs. R=6.5 r=2.1, R=5.9 r=2.3 . IE-2013-6900 . New Caledonia, 25°16’S, 168 °56’E, 750–800m Coll. NORFOLK 2 , DW 2065 1 dry specs. R=5.7 r=1.8 . IE-2013-6901 New Caledonia, 23°43’S, 168 °2’E, 759– 807m. Coll . NORFOLK 2 , DW 2047 1 dry spec. R=5.4 r=2.1 .

Figures

FIGURE 10. Cladaster katafractarius n. sp. IE-2013-17245. R=3.2, r=1.6 cm. A. Abactinal surface. Scale bar=1.0 cm. B. Closeup showing arm, superomarginal plates and arm plates. Scale bar=0.2 cm. C. Actinal surface. Scale bar=1.0 cm. D. Closeup of furrow and adambulacral spines. Scale bar=0.2 cm.

FIGURE 18. Leioastra triangularis n. sp. Holotype IE-2007-3946. r=1.9, r=1.0 cm. A. Abactinal surface. Scale bar=0.5 cm. B. Closeup of arm and superomarginal plates. C. Actinal surface. Scale bar=0.5 cm. D. Closeup of furrow region. Scale bar=0.5 cm.