Sphaeriodiscus mirabilis A.M. Clark 1976

Mah, Christopher L., 2018, New genera, species and occurrence records of Goniasteridae (Asteroidea; Echinodermata) from the Indian Ocean, Zootaxa 4539 (1), pp. 1-116 : 85

Sphaeriodiscus mirabilis A.M. Clark 1976

Figure 33 A–E

A.M. Clark 1976: 248; Mah 2011: 44

Diagnosis. A species of Sphaeriodiscus identified by the presence of ten superomarginals, of which the penultimate plates are enlarged and strongly convex. Secondary plates are present, variably. Four or five furrow spines.

Comments. Larger specimens of this species from Madagascar are approximately the same size (R=7.0, r=4.5) as the type described by A.M. Clark (1976), but differ in having ten superomarginal plates per interradius versus eight in the holotype and four to five furrow spines versus the five listed by A.M. Clark. Of the two specimens representing this species, the dry specimen (IE-2013-6606, R= 7.5 cm) displays a substantially higher number of secondary plates ( Fig. 33D ) on the abactinal surface compared to IE-2007-3988 which shows relatively fewer, these limited to the proximal disk region (R= 6.4 cm). However the wet specimen (IE=2007-3988) has demonstrates much more strongly convex penultimate superomarginals than IE-2013-6606 that are more consistent in size and shape with the other smaller superomarginals.

Consistent with A.M. Clark’s (1976) observation and based on deck shots of the Madagascar specimen, this species is a rich red-orange color.

Occurrence. Vicinity of St. Paul and Amsterdam Islands, South Atlantic (Bouvetoya Island and Tristan de Cunha), Madagascar 195–585

Material Examined. Madagascar. IE-2013-6606 . Madagascar , 12°50’S, 48°9.1’ E, 580–585 m, Coll. A. Crosnier 14 Sept. 1972, 1 dry spec. R=7.5, r=5.3; IE-2007-3988 . Madagascar 26°08’S 45°40’E, 426 m, Coll . ATIMO VATAE, N/O Nosy B e 11 DW 3554 . 1 wet spec. R=6.4 r=4.4

Figures

FIGURE 33. Sphaeriodiscus mirabilis Specimen IE-2007-3988. (except for D). R=6.4, r=4.4 cm. A. Abactinal surface. Scale bar=2.0 cm. B. Closeup showing abactinal plates and granulation. Scale bar=0.3 cm. C. Actinal plate surface. Scale bar=2.0 cm. D. Closeup of dry specimen IE-2013-6606 showing abactinal plates, secondary plates and granulation., Scale bar =0.3 cm. E. Arm tips and superomarginal plate surface. Scale bar=1.0 cm. E. Closeup of furrow and adambulacral spination. Scale bar=0.5 cm.