Stereocidaris excavata Mortensen, 1932b

Filander, Zoleka & Griffiths, Charles, 2017, Illustrated guide to the echinoid (Echinodermata: Echinoidea) fauna of South Africa, Zootaxa 4296 (1), pp. 1-72 : 17

Stereocidaris excavata Mortensen, 1932b

Fig. 12 A–C.

Stereocidaris excavata Mortensen, 1932b . 151–154. Pl. II, Figs 1–5 . Pl. IV, Fig. 2 . Pl. XI, Fig. 1–2 ; Clark & Courtman-Stock, 1976: 217; Schultz, 2011: 1040.

Material examined. MBC-A023320; MBC-A077747; MBC-A077745; MBC-A077748; MBC-A077746; MBC- A077744.

Identification. Similar to Stereocidaris capensis ; but differs in sunken apical disc, which has centrally positioned and slightly raised gonopores. Primary spines slender, somewhat fluted, rugose, with about 12 finely serrate, low ridges; secondaries adpressed, chisel-like in shape. Denuded test creamish, with green tint.

Global maximum size. Maximum test diameter 69 mm.

Global distribution. Endemic to the South coast region of South Africa, at 120–177 m depth ( Mortensen 1932b; Clark & Courtman-Stock 1976; Schultz 2011).

Remarks. Both S. capensis and S. excavata are restricted to South African waters; they may, however, be differentiated by their primary spines and apical discs. S. capensis has fusiform, stout primary spines with 20 longitudinal ridges and an elevated apical disc with distally arranged gonopores; whilst S. excavata has fluted, slender primary spines with 12 low serrations and a distinctively sunken apical disc with centrally positioned, elevated gonopores.

Figures

FIGURE 1. Detail of regular echinoid: upper (Stomopneustes variolaris) and lower (Stereocidaris excavata) side, showing terminology of various body parts.

FIGURE 2. Body plan of an irregular echinoid or sand dollar (Clypeaster rarispinus), showing terminology of various body parts.

FIGURE 3. The body plan of an irregular echinoids or heart urchin (Echinocardium cordatum), showing terminology of different body parts.

FIGURE 4. Tubercle types: A. perforated and non-crenulated (Stereocidaris alcocki). B. non-perforated and non-crenulated (Stomopneustes variolaris). C. perforated and crenulated (Chaetodiadema africanum).

FIGURE 5. Histocidaris elegans (SAMC-A 22212): A. Side view of preserved specimen. B. Apical system of preserved specimen.

FIGURE 12. Stereocidaris excavata (SAMC-A 23320). A. Map showing distribution. B. Side view of preserved specimen. C. Close-up apical system of preserved specimen.