Phorbas posidoni n.sp. (Porifera: Poecilosclerida) from the Aegean Sea,with a discussion of the family Anchinoidae

A new species of the genus Phorbas Duchassaing and Michelotti, 1864 (junior synonym Anchinoe Gray, 1867) is described from the Aegean Sea (Eastern Mediterranean). Phorbas posidoni n.sp. is distinguished from the known Mediterranean species of Phorbas primarily by its elaborate repent-ramose habit combined with an extensive, spongin-enforced, plumoreticulate skeleton of oxea-like tornotes and the usual echinating acanthostyles and arcuate chelae. As in most Phorbas the surface bears characteristic areolae. The only other elaborate Mediterranean species, P. mercator (Schmidt) differs clearly in spiculation, since it lacks microscleres and has strongyles as the main skeletal elements. Phorbas fictitius (Bowerbank), P. tenacior (Topsent) and P. paupertas sensu Topsent are all incrusting and differ in spicule form and sizes as well. Likewise, Phorbas species from the neighbouring East Atlantic each show clear differences with P. posidoni n.sp. The genus Phorbas is discussed and compared with Pronax Gray (1867) sensu Lévi (1973). It is proposed to unite the two genera because the alleged sharp difference between the two (only oxea-like tornotes in the skeletal tracts in Phorbas, only acanthostyles in the skeletal tracts in Pronax) is compromised by a range of intermediate conditions in various species.