Topsent, 1894a
Definition: Demospongiae characterized by a quite uniform spiculation of monaxonid megascleres, usually tylostyles or styles (occasionaly diactines). Microscleres if present, are euasters or streptasters (mostly spirasters) or derivates thereof. The basic architecture is radial, although this arrangement may be limited to the outer layer with a random arrangement of spicules in the interior. The peripheral megascleres may constitute a smaller size category and are often oriented perpendicular to the surface with the pointed ends protruding, and these provide a plush-like surface. Intercellular collagen fibrils are abundant, and moderate to small amounts of spongin join the megascleres together. A well-formed network of spongin fibres is absent, however, so that the consistency of Hadromerida is firm but often friable (Polymastia mamillaris skel) (Suberites domuncula) (anthosigma).
Remarks: Oviparity is the rule in Hadromerida, with development taking place outside the sponge. The larval type is parenchymella, except in Polymastia , which has a modified blastula larva that creeps over the substrate.
Hadromerida are encrusting, massive, spherical or stipitate. They are common in all seas from the intertidal to depths of at least 4000 m. This order comprises several distinct families, but the exact number is still undecided. Valid families recognized here are:
Family Polymastiidae: with cortex and papillae.
Family Suberitidae: no cortex.
Family Stylocordylidae: stalked; with centrotylote oxeas.
Family Clionidae: excavating, with papillae; spirasters.
Family Spirastrellidae: no papillae; spirasters.
Family Latrunculiidae: sceptrum microscleres (also dubbed discorhabds or discasters).
Family Placospongiidae: with selenasters and spirasters.
Family Timeidae: with euasters (e.g. anthasters) and diplasters.
Family Tethyidae: with cortex; strongyloxeas and diversity of euasters.
Family Hemiasterellidae: controversial Hadromerida, formerly considered an Axinellida family; now associated with other aster-bearing Hadromerida: with euasters and styles.
Source: Hooper's Internet Sponge Guide.
Families not treated here:
Family Latrunculiidae —Latrunculia cratera Bocage (1869) and Latrunculia triloba (Schmidt, 1875), cf. Arndt, 1935: 37, figs. 59, 60.
Family Stylocordylidae —Stylocordyla borealis (Loven, 1868), deep water Norway; cf. Arndt, 1935