A re-appraisal of the holothuroid genera Pseudocnus Panning, 1949 and Pseudocnella Thandar, 1987 based on morphological and, for the latter, also molecular evidence (Echinodermata : Holothuroidea : Dendrochirotida : Cucumariidae)

Abstract

After the erection of the genus Pseudocnella by Thandar (1987) to accommodate three southern African Cucumariids and a Mediterranean form, then classified in Pseudocnus, certain problems still remained. In addition to this the recent revision of the Antarctic-Subantarctic species of Pseudocnus by O’Loughlin et al. (2014) left the remaining world species unattended to. Due to the above, both these genera (Pseudocnus and Pseudocnella) were looked at critically in order to determine whether all species assigned to them are congeneric. As far as the genus Pseudocnus is concerned those species excluded from O’Loughlin et al (2014) revision are looked at only morphologically by examining available materials and literature. Species belonging to the genus Pseudocnella are examined from both morphological and molecular aspects. O’Loughlin et al. (2014) restriction of the genus Pseudocnus was accepted and hence two new genera Panningocnus and Thandarocnus are diagnosed for those species with unequal tentacles and body wall deposits respectively made up of a single or more than a single layer of calcareous material. On this basis only three species now remain in Pseudocnus, with Cucumaria koellikeri Semper, 1868 as type species, nine species are transferred to Panningocnus, with Cucumaria dubiosa Semper, 1868 as type species and the remaining six species transferred to Thandarocnus with Pseudocnus sentus O’Loughlin & Alcock, 2000 as type species. A new genus Hemiocnus is erected for Cladodactyla syracusana Grube, 1840 (=Pseudocnella syracusana) as type species and to this is also transferred Pseudocnella insolens (Théel, 1886). The genus Pseudocnella now appears to accommodate only two South African nominal species with Cucumaria sinorbis Cherbonnier, 1952 remaining as type species. All species dealt with are diagnosed, keyed and their geographical distributions mapped, except those dealt with by O’Loughlin et al. (2014) and Thandar (1987).