Zootaxa 4466 (1): 197–204 ISSN 1175-5326 (print edition) http://www.mapress.com/j/zt/ Article ZOOTAXA Copyright © 2018 Magnolia Press ISSN 1175-5334 (online edition) https://doi.org/10.11646/zootaxa.4466.1.15 http://zoobank.org/urn:lsid:zoobank.org:pub:1BCC4BD8-A168-408A-8DFD-407DFA44C91D When is an aster not an aster? A new deep-sea Discorhabdella (Demospongiae, Poecilosclerida) with asters, from the Mozambique Channel JEAN VACELET1,3 & PACO CÁRDENAS1,2 1IMBE, CNRS, Aix Marseille Univ, Univ Avignon, IRD, Station Marine d’Endoume, 13007 Marseille, France. 2Pharmacognosy, Department of Medicinal Chemistry, Uppsala University, Uppsala 75123, Sweden. http://orcid.org/0000-0003- 4045-6718 3Corresponding author. E-mail:
[email protected] Abstract Discorhabdella pseudaster n. sp. is an incrusting sponge from the upper bathyal zone of the ‘Banc du Geyser’, north of Madagascar, Mozambique Channel. This new species is described only from a single specimen but it is remarkable by the presence of spicules similar to euasters, a type of microsclere unknown in Poecilosclerida. These spicules are in fact a new example of homoplasy, being derivatives of the typical Discorhabdella pseudoastrose acanthostyles, which are here re- duced to the aster-like tyles. The isochelae with a large lamella on the shaft are also quite unique in Poeciloclerida. Key words: Porifera, new species, Madagascar, bathyal, homoplasy Introduction The Mozambique Channel is still a poorly explored area for Demospongiae, despite the works of Bösraug (1913), Lévi (1956, 1964), Vacelet & Vasseur (1965, 1971) and Vacelet et al. (1976), Vasseur & Lévi (1976) who collected extensively in W Madagascar and Europa Island.