Two new genera and a new species in the holothurian family Cucumariidae (Echinodermata: Holothuroidea)

Abstract

Two new genera, Trachycucumis and Trachasina, in the holothurian family Cucumariidae, are described. The former is erected to accommodate a new southern African cucumariid, here described as T. plettenbergi, from the southeast coast of South Africa, and the Trachythyone sp. Thandar (1991) from the northeast coast. Trachasina is currently monotypic and is erected to accommodate Trachythyone crucifera (Semper, 1869) which has remained erroneously in Trachythyone for so long, despite several reservations. Trachycucumis differs from Trachythyone in being a warm-water genus with body wall spicules in the form of spinous cross-shaped rods and multilocular plates with one end often prolonged as a spinous handle. The new species, T. plettenbergi differs from Thandar’s Trachythyone sp. in the absence of rosette-shaped deposits and the simplicity of the plates. Trachasina, on the other hand, is unique in having 10 equal tentacles and sparsely distributed spicules in the form of spinous crosses, unlike those of Trachycucumis, and simple, thick, smooth, oval plates with few perforations and without any prolongations.