Phormosoma placenta africana Mortensen, 1934a

Filander, Zoleka & Griffiths, Charles, 2017, Illustrated guide to the echinoid (Echinodermata: Echinoidea) fauna of South Africa, Zootaxa 4296 (1), pp. 1-72 : 25-26

Phormosoma placenta africana Mortensen, 1934a

Fig. 23 A–C.

Phormosoma placenta, var. africana: Mortensen, 1934a: 162 .

Phormosoma placenta africana: Clark & Courtman-Stock, 1976: 221 . Phormosoma placenta: H.L. Clark, 1923 *: 374–375; H.L. Clark, 1924: 4; H.L. Clark, 1925a: 54; Schultz, 2011: 1073, Figs 1869–1870.

Material examined. MBC-A 022220; MBC-A 022241; MBC-A 022242; MBC-A 022243; MBC-A 022244; MBC- A 022245; MBC-A 022246; MBC-A 022247; MBC-A 022249; MBC-A 022250; MBC-A077775; MBC-A077776; MBC-A077777.

Identification. Differs from Phormosoma busarium in having straight aboral primary spines. Low hemispherical test with sharp margin. Small tubercles are surrounded by large areoles on oral side; aborally tubercles in an irregular arrangement, where areoles are not deepened.

Global maximum size. Maximum test diameter 120 mm.

Global distribution. P. placenta is a widely-distributed Atlantic species, while the South African subspecies, P. placenta africana is restricted to the Southern Atlantic, at 50 – 3700 m depth range.

Remarks. Mortensen (1935) distinguished the South African P. placenta from the Atlantic P. placenta because of the presence of large tubercles, which suggests larger spines and the feature of species reaching a considerably larger size. Therefore he placed South African P. placenta in the separate subspecies, P. placenta africana . Differs from P. bursarium in having a distinctive sharper outline and finer tubercles, and by geographic distribution— P. bursarium being known from the Indian Ocean and P. placenta from the Atlantic Ocean.

Figures

FIGURE 23. Phormosoma placenta africana (SAMC- A 22250). A. Map showing distribution. B. Aboral view of preserved specimen. C. Oral view of preserved specimen.