Order Hadromerida Topsent, 1894

Abstract

Hadromerida Topsent (Demospongiae), including Clavulina Vosmaer and Astromonaxonellida Dendy, contains 23 nominal families or subfamilies of which 13 families are recognised here (two allocated as incertae sedis). The order includes sponges with monaxonic megascleres (tylostyles, subtylostyles, oxeas or derivatives) producing radiate or subradiate skeletal arrangement, although this arrange- ment may be obvious only in the peripheral skeleton in some, often with scarce spongin and consequently firm, non-elastic consistency. Ectosomal spicules are often smaller than choanosomal ones, and where present these may form a prominent cortical skeleton. Microscleres may include various forms of euasters, spirasters, rhabds, microxeas and/or raphides, although many hadromerids lack microscleres altogether. Hadromerid sponges are known from all oceans at all depths.