Cyamon Gray, 1867

Soest, Rob van, Carballo, Jose Luis & Hooper, John, 2012, Polyaxone monaxonids: revision of raspailiid sponges with polyactine megascleres (Cyamon and Trikentrion), ZooKeys 239, pp. 1-70 : 4-6

Genus Cyamon Gray, 1867

Type species:

Dictyocylindrus vickersii Bowerbank, 1864 (original designation).

Definition

(emended): Cyamoninae with skeleton consisting of a basal mass of polyactine spicules of which one or more cladi are spined or rugose in mature condition, supporting a plumose choanosomal skeletal arrangement of single or columnar groups of styles or subtylostyles with pointed ends outwards. Additional longer and shorter thin styles may be present in peripheral regions.

Remarks.

The styles are usually smooth, but in Cyamon spinispinosum (Topsent, 1904) both shorter and longer styles are spined (see below). In the type species, and several other species, thin short styles take the form of angulated and/or centrotylote strongylostyles, some of which have one end faintly or more heavily spined (see below). Polyactine spicules are genuinely polyaxone, with axial canals visible in all cladi. They are predominantly calthrops-like and have four cladi, but this may vary between two and eight cladi in some species. Usually, one of the cladi differs from the others by having a pointed spined apex, whereas the other cladi frequently have rounded ends, with prominent spined bulbs in several species, or they are occasionally entirely smooth, differing frequently also in length (either longer or shorter) from the other cladi. The spined pointed cladus is termed ‘basal’, under the assumption that it is homologous to the shaft of an ancestral echinating acanthostyle. The remaining cladi are here termed ‘lateral’, based on the assumption they are lateral proliferations of the acanthostyle head. One of the new species described below, has the polyactine spicules in two distinct categories, the smaller one of which is ‘amphipolyactine’ (see below).

Trikentrion Ehlers, 1870 shares the polyactines with Cyamon . According to the latest treatment of both genera (Hooper, 2002) the polyactines of Cyamo n would have all the cladi spined, whereas those of Trikentrion would have only the basal cladus spined. If this distinction between Cyamon and its close relative Trikentrion in the cladus spination would be maintained, then four species originally described as members of Cyamon would need to be transferred to Trikentrion , Cyamon quinqueradiatum , Cyamon neon de Laubenfels, 1930, Cyamon argon Dickinson, 1945 and Cyamon catalina , as well as one of the new species described below. We will demonstrate below and in the Discussion that cladus spination does not coincide with other more compelling differences with Trikentrion and consequently we will not transfer (all) the mentioned taxa.

The species considered valid members of Cyamon are listed in Table 1 and their properties in Table 2.