Topsent, 1928
Definition: Persistently encrusting growth form. The oscules and ostia may be borne on papillae and raised areolated porefields. Spined bases of intermingled large choanosomal styles and smaller acantho-styles are embedded in a basal layer of spongin, standing perpendicular to the substrate. Smooth, often polytylote, diactinal tornotes, anisotornotes or oxeas, or sometimes monactinal spicules (styles), occur singly or form bundles on the surface. Microscleres include arcuate or unguiferous isochelae, and sigmas. Toxas never present.
Remarks: This is a suspect family as the thinly encrusting growth form seems to be the only discriminating character. Emphasis is placed on the presence of larger structural acanthostyles and smaller echinating ones. Forms with palmate or anchorate chelae and with forceps are referred to other families.
For the time being the family Anchinoidae is kept separate, but this will eventually be merged into Hymedesmiidae.
21 nominal genera are presently included in this family, although only 12 are recognised here.
Source: Hooper's Internet Sponge Guide.
Genera represented in the area:
Hymedesmia Bowerbank, 1863 (type species H . zetlandica Bowerbank, 1863) (syn. Sclerilla Schmidt, 1868; Hymenamphiastra de Laubenfels, 1930; Ferrerhernandezia de Laubenfels, 1936; Hymoxenia Alander, 1938; Quindesmia de Laubenfels, 1950; Stylopus Fristedt, 1885): encrusting; ectosomal skeleton composed of smooth ectosomal anisotornotes; choanosomal skeleton with hymedesmoid skeleton, composed of one or two sizes of acanthostyles erect on the substrate; microscleres are arcuate isochelae or anisochelae and sigmas.
Spanioplon Topsent, 1890 (type species Hymeniacidon armatura Bowerbank, 1866) (syn. Acanthoxa Hentschel, 1914; ?Spirorhabdia Schmidt, 1875): oscules grouped in sieve plates; ectosomal skeleton composed of smooth anisotornotes, smooth or microspined choanosomal styles, small acanthostyles or acanthoxeas dispersed (possibly homologues of echinating spicules or true microscleres), chelae absent.
Species included:
Hymedesmia areolata
Hymedesmia baculifera
Hymedesmia basispinosa
Hymedesmia coriacea (=H. brondstedi )
Hymedesmia crux
Hymedesmia jecusculum
Hymedesmia lenta
Hymedesmia mamillaris
Hymedesmia minuta
Hymedesmia occulta
Hymedesmia pansa
Hymedesmia paupertas
Hymedesmia peachi
Hymedesmia pilata
Hymedesmia primitiva
Hymedesmia veneta
Hymedesmia versicolor
Hymedesmia zetlandica
Spanioplon armaturum
Species not treated here:
Hymedesmia clavigera (Levinsen, 1887), Norway, cf. Arndt, 1935: 65, fig. 123
Hymedesmia consanguinea Lundbeck, 1910, Greenland, Galicia, cf. Cristobo et al., 1998: 177 (too late to incorporate in the present version)
Hymedesmia curvichela Lundbeck (1910), Ireland, Iceland, Norway, cf. Stephens, 1920
Hymedesmia filifera (Schmidt, 1875), Norway, cf. Arndt, 1935: 66, fig. 126
Hymedesmia koehleri (Topsent, 1896), Ireland, Bay of Biscay, cf. Stephens, 1920: 34
Hymedesmia longistylus Lundbeck (1910), Norway, Iceland, cf. Burton, 1930a: 494
Hymedesmia mucronata (Topsent, 1904), Ireland, Norway, cf. Stephens, 1920: 39
Hymedesmia mucronella Lundbeck, 1910, Iceland
Hymedesmia mutabilis (Topsent, 1904), Ireland, Norway, cf. Stephens, 1920: 38
Hymedesmia norvegica Thiele (1903), Norway, cf. Arndt, 1935: 67, fig. 128
Hymedesmia nummulus, Hymedesmia nummulus habit Lundbeck (1910), Iceland
Hymedesmia perforata Lundbeck (1910), Iceland
Hymedesmia procumbens Lundbeck (1910), Iceland
Hymedesmia rugosa Lundbeck (1910), Iceland
Hymedesmia similis Lundbeck (1910), Iceland, Norway, cf. Burton, 1930a
Spirorhabdia (= ?Spanioplon )vidua (Schmidt, 1875), Norway, cf. Arndt, 1935; 43, fig. 73.