Scopalina Schmidt 1862

Definition: Thinly or thickly encrusting; soft and compressible; few or no ectosomal spicules; spongin abundant, with extensions of spongin manifest as mounds or fibers arising from basal spongin plate; these fibers may branch and merge; choanosomal skeleton of spicules or spicule bundles with proximal ends or entire spicule enclosed in spongin; choanosome may have a grainy appearance. Larvae are elongated, conical; anterior region wider than the posterior zone; completely covered by short cilia. (Modified from Blanquer and Uriz 2008).

Diagnosis: Scopalina have abundant spongin, while Svenzea are described as having limited spongin, primarily at the nodes of a reticulated spicule network. Svenzea tend to have shorter spicules, (200–300 µm), whereas in Scopalina they mostly range from 400 to 2000 µm (though S. canariensis averages only 199 µm). The skeletal architecture of Svenzea has been noted as more like that of the haplosclerida than Scopalina . Svenzea are massive or thickly encrusting, while Scopalina are thinly to thickly encrusting.

Stylissa are erect, flabellate, or lobate, rather than possessing encrusting morphologies seen in Scopalina . Stylissa are noted as having a skeletal architecture like that of the Halichondridae, with many spicules in confusion.