Schmidt, 1870
Definition: Myxillina with anchorate or unguiferate chelae, and diactinal (normally oxeote) megascleres. No morphological differentiation in ectosomal and choanosomal megascleres (Desmacidon fruticosum spics).
Remarks: Encrusting, massive, lobate, fan-shaped or branching sponges. The ectosomal skeleton consists of perpendicular bundles or bouquets of megascleres and numerous microscleres. The bouquets of megascleres may also be at the end of longer subectosomal spicule bundles traversing larger subdermal lacunae. Choanosomal skeleton reticulated, either an isodictyal network making small meshes one spicule in length and width, or forming a coarser mesh in an anisotropic reticulation of thick spicule tracts.
The taxonomic history of Desmacididae is complicated and full of erroneous assumptions and decisions, as was explained at length by Hajdu et al., 1994. This was the reason for these authors to make a case for abandoning this name. However, since it is one of the oldest names in sponge systematics, and since the priority rule also applies to family names, it is not possible to manoevre it into synonymy. It is here proposed to restrict the use of the family name to Desmacidon and its immediate relatives Desmapsamma , despite the similarity (microscleres) of Desmacidon to Myxilla in the family Myxillidae. Justification is found in the apparent suppression of choanosomal megascleres in favour of the ectosomal tornotes, which are also smooth oxeotes.
The possession of only tornote-derived spicules is shared with genera such as Fibulia , Amphiastrella, several Coelosphaeridae and most Phoriospongiidae. From these, members of Desmacididae differ in having a reticulate skeleton and anchorate chelae. References: Hajdu et al., 1994; Desqueyroux-Faúndez and Van Soest, 1996
Source: Van Soest, unpublished.
Genus represented in the area:
Desmacidon Bowerbank, 1861 (type species Spongia fruticosa Montagu, 1818): erect growth forms; ectosomal skeleton composed of smooth oxeote spicules arranged in bouquets; choanosomal skeleton composed of smooth diactinal megascleres forming an isodictyal reticulation; microscleres are spatuliferous anchorate isochelae and sigmas.
Species included:
Desmacidon fruticosum