Definition: Tubular, spherical, flask-shaped, ovoid and branching growth forms, and occur as solitary sponges or in groups. Ectosomal cortex is continous and strengthened by tangential spicules, but these do not cover the choanocyte chamber layer. Choanosomal spicules, supporting choanocyte chambers, have an articulated arrangement of overlapping sagittal triactines, with the angle between the paired rays larger than the angles between each paired ray and the long, unpaired ray. The sagittal triactines have the longest ray pointing to the exterior of the sponge, and form a layer beneath the spongocoele lining (referred to as the subgastral position). Collar-cells usually confined to the radial chambers in the adult, and probably always with apical nuclei. Choanocyte chambers are syconoid, arranged radially around a central cavity (spongocoel), and the ends of chambers project to a greater or lesser extent on the ectosomal surface. (syconoid system) (Sycon ciliatum cross).
Remarks: There are only two valid genera included in this family, only one occurs in the area.
Source: Borojevic et al. 2002b.
Genera represented in the area:
Sycon Risso, 1826 (type species Spongia ciliata Fabricius, 1780) (syn. Scypha Gray, 1821; Calcispongia Blainville, 1830; Calcepongia Lamarck, 1836; Dunstervillia Bowerbank, 1845; numerous further synonyms, especially by Haeckel, 1870): tubular, spherical to elongate and cylindrical; surface minutely papillate and hispid; apical oscule with or without fringe; texture soft to firm; tubar skeleton of basal rays of subgastral sagittal triactines and several rows of tubar sagittal or subregular triactines, and ectosomal surface with distal cones ornamented with oxeas; choanosomal skeleton of paired rays of subgastral sagittal triactines and choanosomal sagittal or subregular triactines and tetractines; skeleton of chamber layer typically articulate and showing no marked differences in size between radiates of ectosome, chamber layer and choanosome except where tubar skeleton is reduced to sagittal subgastral triactines (Burton, 1963 as Scypha).
Species not treated here:
Sycon boreale (Schuffner, 1877), Norway, uncertain status, cf. Arndt, 1935: 10.
Sycon schuffneri Dendy and Row, 1913,(for Sycandra quadrata sensu Schuffner, 1877), Norway, uncertain status, cf. Arndt, 1935: 13.
Sycon sycandra: Borojevic et al., 1968: 34 (supposedly Homoderma sycandra Von Lendenfeld, 1885: 1088, pl. 40 fig. 14, pl. 43 figs. 16-21, pl. 45 figs. 21-33, recorded originally from Australia), Roscoff, uncertain status.