Order Poecilosclerida Topsent, 1928

Abstract

Poecilosclerida Topsent (Demospongiae) contains the highest diversity of species and possibly the greatest range of morphometric char- acters of all Porifera, with 25 families, 129 genera and 50 subgenera recognised as valid, and several thousands of described species worldwide, distributed from intertidal to abyssal depths. Four suborders are delineated based primarily on: chelae geometry (palmate- arcuate-anchorate forms, and diancistra derivatives); presence/absence of discate microrhabds; presence/absence and geometry of other microscleres; ectosomal megasclere geometry; and choanosomal megasclere diversity, geometry and regionalisation of megascleres within the skeleton. The order is defined as containing demosponges with discrete organic and inorganic skeletons, with discrete siliceous spicules, a skeletal organisation commonly localized to particular regions (at a minimum ectosomal and choanosomal skeletons but poten- tially containing up to five regionally differentiated megasclere morphologies), microscleres consisting of meniscoid spicules (sigmas and derivatives such as chelae, sigmancistras, diancistras, etc., with chelae synapomorphic for the order, although not all taxa contain them), in addition to diverse other forms such as toxas, forceps, onychaetes, raphides (in trichodragmata), microrhabds, acanthomicrorhabds, anisodiscorhabds, isochiadiscorhabds, spinorhabds, thraustoxeas, spirosigmata, thraustosigmata and microstyles.