Van Soest n. fam.
Definition: Encrusting , massive, fistular, ramose or flabellate Myxillina; ectosomal skeleton variously consisting of perpendicular or tangentially arranged tornotes or absent; many genera demonstrate a lack of differentiation of megascleres. Choanosomal skeleton reticulate or hymedesmoid. Choanosomal megascleres styles or strongyles, smooth or acanthose. Microscleres birotulates, occasionally also anchorate isochelae and sigmas.
Remarks: This is a recently proposed family uniting all Poecilosclerid sponges with birotulate microscleres (double-umbrella chelae). The variability of growth forms and skeletal structures paralles that of other large Myxilline families such as Myxillidae and Coelosphaeridae. 12 nominal genera, comprising 8 valid genera, are included.
Source: Van Soest, in preparation.
Genera represented in the area:
Hymetrochota Topsent, 1904 (type species H . rotula Topsent, 1904) (syn. Hymenotrocha Burton, 1930a): hymedesmioid arrangement of megascleres, including echinating acanthostyles erect on the substrate.
Iotroata de Laubenfels, 1936 (type species Iotrochota acanthostylifera Stephens, 1916) (syn. Iotaota de Laubenfels, 1936): encrusting, massive or flabellate; ectosomal skeleton composed of smooth ectosomal tylotes with mucronate or spined ends, mostly standing erect, sometimes paratangentially, in bundles on the surface; choanosomal skeleton composed of smooth or slightly acanthose styles, sometimes oxeote or absent, forming an isotropic reticulation; fibres are poor but there may be abundant collagen; microscleres are birotulates, anchorate (unguiferous) isochelae and sigmas.
Rotuloplocamia Lévi, 1952 (type species R . octoradiata Lévi, 1952): with basal reticulation of acanthostrongyles on the nodes of which long styles stand erect surrounded by short acanthostyles. Tornotes are anisostrongyles or subtylotes arranged in erect bundles. Microscleres birotules.
Species included:
Iotroata spinosa
Rotuloplocamia octoradiata
Species not treated here:
Hymetrochota topsenti (Burton, 1930a), Norway, cf. Arndt, 1935: 61, fig. 114
Iotroata abyssi (Carter, 1874), Norway, Shetland, cf. Arndt, 1935: 64, fig. 121.