Iphiaster noemieae, 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 : 44-47

Iphiaster noemieae n. gen, n. sp.

Figure 16 A–F

Type species. Iphiaster noemieae , n. gen, n. sp. by monotypy.

Etymology. The genus is named for the Greek Iphios meaning “strongly or mightily” and - aster for “star” alluding to the well-developed skeleton in this taxon.This species is named for colleague Noémie Vasset (1986–2016), a researcher at the Muséum national d'Histoire naturelle in Paris.

Diagnosis. A species distinguished by a stout, stellate body form (R/r=1.97–2.29) ( Fig.16A ), with weakly developed abactinal, tabulate plates forming shallow fasciolar grooves ( Fig. 16B ). Surface covered by coarse, round granules covering each plate, approximately 1.5–2.0 granules present along a 1.0 mm line. Center of most abactinal plates with a small, tong-like pedicellariae ( Fig. 16B ). Superomarginal plates forming well-developed abactinal periphery with an irregularly shaped bald patch on each plate, peppered with widely spaced coarse granules ( Fig. 16C ), approximately 15–50. Distalmost five superomarginal plates directly abutting over midline ( Fig 16A ). Actinal plates covered by round to pointed widely spaced, granules, six to 50, mostly 20–40. A single paddle-shaped pedicellariae, identical to those on other surfaces, present on 20–40% of plates on actinal surface. Pedicellariae especially prominent adjacent to adambulacral plate series ( Fig. 16F ). Furrow spines five or six, subambulacral spines three or four.

Comments. Iphiaster noemieae n. gen. n. sp. displays characters which do not permit placement within any pre-existing goniasterid genera. Iphiaster noemieae n. gen. n. sp. shows some similarities with the South African Toraster tuberculatus in that the abactinal and actinal surfaces are partly or completely covered by coarse, round granules ( Fig. 16B ), a stout abactinal and marginal skeleton are present, and fasciolar grooves among the abactinal plates are present.

Iphiaster n. gen. differs in several respects from the summary diagnosis for Toraster Mah (2006) , including the absence of smooth, convex abactinal and marginal plates, presence of granules scattered on the central surface of the superomarginal plates, presence of abutted superomarginal plates, absence of large abactinal and marginal pedicellariae, and the difference in marginal plate shape between Toraster which have primarily rounded edges versus Iphiaster n. gen., which has angular marginal plate edges. The fasciolar grooves and the round, coarse granules in Iphiaster are very similar to Toraster suggesting closer relationship. Toraster is also known from the adjacent South African region. However, the pedicellariae type, the marginal plate shape, displaying a quadrate shape and marginal surface with scattered, coarse granules as well as the strong abactinal facing and abutted superomarginals along the arm are similar to those in Astroceramus .

Occurrence. Southwestern Indian Ocean, Walters Shoal, 964–1052 m.

Description. Body stellate (R/r=1.97–2.29) with triangular arms narrowing acutely to pointed tips. Interradial arcs broadly curved ( Fig. 16A, E ). Interradial regions with gently sloping dorsolateral angle becoming more distinctly angular distally along arms.

Abactinal region composed of low, weakly tabular plates with surfaces round to polygonal in outline. Plates larger on disk center and along radial regions becoming smaller and more closely arranged interradially. Fasciolar grooves very shallow, becoming practically non-existent interradially. Each plate covered by densely arranged, coarse, round granules approximately 1.5 to 2.0 granules counted along a 1.0 mm line ( Fig. 16B ). Approximately 10–50 per plate, but most with 20–40 homogeneous granules. Granular cover is denser interradially, more widely distributed proximally and along radial regions. There is little to no distinction in morphology between peripheral and central granules, but the apical concavity of each plate elevates the central granules relative to the peripheral granules. Approximately 30–40% of the total number of granules are present peripherally. A majority (>70%) of abactinal plates bear one or two large (1.0– 1.5mm length) paddle-shaped pedicellariae present centrally on each plate ( Fig. 16B ). Pedicellariae when present reside within shallow pits present on surface, these regions enlarged with no granules present on surface of plate adjacent to pedicellariae. Approximately 60% of pedicellariae with a granule-free smooth surface present around it. Madreporite weakly convex, well developed sulci present, quadrate in shape, flanked by four abactinal plates.

Marginal plates, 20–24 per interradius (arm tip to arm tip) on individuals varying between 5.7 to 6.1. Inferomarginals offset from superomarginals forming zigzag contact between them. On all individuals examined, distalmost superomarginals, varying from 5 to 7 pairs, abut over midline of arm ( Fig. 16A ). Contact between abutted superomarginals offset forming jagged contact between them. Superomarginal plates elongate interradially becoming wider distally but angular and quadrate in outline throughout. Superomarginal abactinal surface relatively flat sitting on same plane as abactinal surface and forming part of the abactinal facing of the disk surface. Of the interradial radius (r=3.1) the superomarginal periphery forms (0.6/3.1) approximately 19–20% of the total “r” distance. Each superomarginal plate with 30 to approximately 350 (mostly 50 to 150 per series) peripheral granules, with interradial plates displaying two series around each plate. Granules are coarse and round, consistent in shape and size with those on abactinal plates and form a continuous cover with them. Superomarginal plate surface with quadrate to polygonal bare surface on the abactinal surface with one to 75 (mostly 15–50) widely distributed granules scattered on smooth, bare region ( Fig. 16C ). Granules disappear almost completely on distalmost three to four superomarginal plates. Lateral face of superomarginal plates adjacent to abactinal face completely covered by densely arranged coarse, round granules, approximately 100–250, identical to those on abactinal surface and on bare abactinal region. These lateral-facing granules gradually decrease in number and distribution and disappear completely distally on arm tips. Bare regions, devoid of granules present on a minority of interradial superomarginal plates as they transition to distalmost superomarginals with complete absence of granules. Distalmost superomarginals weakly tumid with pronounced convex surface adjacent to arm tips. Pedicellariae, one to five, paddle-shaped approximately 1.0 mm in length. Pedicellariae present with most abundance interradially but are present with greatest number, two widely spaced from one another, adjacent to contact with abactinal plates and on lateral surface of superomarginal plates. A minority of pedicellariae forming bare surfaces interrupting the granular surface ( Fig. 16C ). Superomarginal plate series in one individual with irregular plate present between others in series, possibly the result of sublethal predation. Terminal plate, large, triangular with smooth surface, lacking accessories (no granules, etc.) with distinct conical spine tip. Inferomarginals covered by coarse, round granules 200–400 almost completely covering lateral and actinal inferomarginal plate surface. Granules gradually disappear on the three to four distalmost plates. Interradial inferomarginal plates with bare regions, variably shaped, ranging from “J” shaped raised strip to quadrate/round shaped bare region covered with scattered 10–18 (mostly 13–15) coarse granules scattered on surface. Pedicellaria, one or two identical to those elsewhere on body present on inferomarginals. Granular covering on actinal surface of inferomarginals continuous with those on actinal surface.

Actinal surface with two to three full series in chevron-like pattern, individual plates quadrate to irregular in shape. Actinal plates covered by six to 50, mostly 20–40, widely-spaced, coarse heterogeneously sized granules ( Fig. 16D, E ). Most are rounded but some with blunt tips. A single paddle-shaped pedicellaria, identical to those on other surfaces, present on 20–40% of plates on actinal surface ( Fig. 16F ). Pedicellariae especially prominent adjacent to adambulacral plate series. Shallow fasciolar groove present between actinal plates.

Furrow spines five or six, finger like, elongate, round to quadrate in cross-section, each series interdigitating with furrow spines on complimentary side ( Fig. 16F ). Furrow spines proximalmost to oral region approximately 50% of height of other furrow spines. Distalmost furrow spines thickest, but comparable in size to other furrow spines. Subambulacral spines set off from furrow spines by distinct space, series immediately behind furrow spines composed of three or four spines approximately half the height of the furrow spines approximately twice as thick. On one individual, a simple pedicellariae replaces the proximalmost subambulacral spine. Remainder of adambulacral plate accessories in irregular series ranging from a single or double jumbled series composed of four to 20 (mostly eight or nine) pointed granules similar in height to those on actinal plate surface but approximately twice as thick, ranging from round to triangular in cross-section. Subambulacral spine/granules on adambulacral plates widely spaced from one another.

Oral plates with furrow spines eight or nine, quadrate to triangular in cross-section, widely spaced with one distinct, enlarged spine, triangular in cross-section projecting into mouth per plate (thus, two per interradius) ( Fig. 16D ). Oral plate surface with two series of six to seven short, triangular in cross-section, pointed granules, each matching one another across the tissue covered contact between the two halves central to the oral plate. Remainder of each plate with 10–12 thick, round to triangular in cross-section pointed to round granules, widely spaced from one another.

Color in life deep orange.

Material Examined. Holotype: MNHN IE-2013-17137 . Southwestern Indian Ocean , Walters Shoal, 33° 31'S, 43° 60' E to 33° 32’'S, 43° 60' E, 1000–1052 m. Coll. MD208 , CP 4905, May 9, 2017. 1 wet spec. R=6.1 r=3.1. Paratypes: MNHN IE-2013-17147 . Southwestern Indian Ocean , Walters Shoal, 32° 46' S, 44° 17' E to 32° 46' S, 44° 18' E, 965– 964 m. Coll . MD208 , CP 4911 10/5/17. 2 wet specs. R=6.3 r=3.0 R=5.7 r=2.9

Figures

FIGURE 16. Iphiaster noemieae n. gen, n. sp. Holotype IE-2013-17137. r=6.1, r=3.1 cm. A. Abactinal surface. Scale bar=3.0 cm. B. Closeup showing abactinal plate detail. Inset shows pedicellariae (each 0.1 to.15 cm in length). Scale bar=0.5 cm. C. Superomarginal plate detail showing bald patch with pedicellariae and granules. Scale bar=0.5 cm. D. Oral region. Scale bar=0.5 cm. E. Actinal surface. Scale bar=3.0 cm. F. Furrow spines and adjacent adambulacral region. Scale bar=0.5 cm.