Stolus kilberti, a new species from the east coast of South Africa (Echinodermata: Holothuroidea: Dendrochirotida) with a key to the genus Stolus Selenka

Abstract

A new species of phyllophorid dendrochirotid, collected from subtidal waters off the east coast of South Africa, is described as Stolus kilberti sp. nov. in the subfamily Thyoninae. It is distinctive in the form of its calcareous ring and body wall plates in combination, and appears to be closely related to S. rapax (Koehler & Vaney, 1908) from the Bay of Bengal, differing from it in having elongated, rather than spherical multi-layered plates If the calcareous ring were not fragmented the species could well be referred to the genus Pseudothyone Panning, 1949 of the subfamily Sclerodactylinae, closely allied to P. mosaics (Koehler & Vaney, 1910) from the Persian Gulf. The remarkable similarity in the body wall deposits of genera currently classified in two separate subfamilies challenges the use of the calcareous ring to separate subfamilies, since it demands a degree of evolutionary convergence which hardly seems probable. Of the eleven nominal species of Stolus, eight are keyed and a table provided to compare the three similar species - S. kilberti, S. rapax and P. mosaica.