Suborder Microcionina Hajdu, Van Soest & Hooper, 1994

Abstract

Microcionina Hajdu et al. (Demospongiae, Poecilosclerida) contains 42 valid genera, 19 subgenera and over 1,000 described species of sponges worldwide, with many more species awaiting description. The suborder is characterised in having terminally microspined ecto- somal megascleres and up to five categories of structural megascleres, most frequently monactinal or derivatives from these, and microscleres that include palmate chelae and diverse toxas, but never sigmas. Four families are included: (1) Microcionidae (viviparous) with principal (subtylo)styles coring spongin fibres, echinating (acantho)styles perpendicular to fibres, and one or more category of acces- sory (subtylo)styles forming a peripheral or extra-fibre skeleton, with microscleres palmate isochelae and diverse forms of toxas. (2) Acarnidae (viviparous) with an ectosomal skeleton of basally spined tylotes arranged tangentially, with monactinal choanosomal megascleres (styles) coring fibres, with or without echinating spicules, and microscleres palmate isochelae and toxas sometimes with others such as bipocillae, modified anisochelae, microrhabds and raphides. (3) Raspailiidae (oviparous) often with some degree of axial compression of the skeleton, typically with a hispid surface produced by brushes of small ectosomal megascleres surrounding protruding choanosomal megascleres, diverse geometric modifications to echinating megascleres, and lacking microscleres other than raphides (trichodragmata) in a few genera. (4) Rhabderemiidae (presumed oviparous) with rhabdostyles bearing a basal spiral twist, and peculiar microscleres (perhaps superficially) resembling toxas (thraustoxeas), sigmas (spirosigmata, thraustosigmata) and rugose microstylote spicules, and lacking chelae.