Marine Biodiversity » Marine Sponges » Calcarea » Calcarea Classification » Subclass Calcaronea

Definition: Encrusting and lamellate growth forms; oscules may be supported by di-, tri- and tetractinal spicules; choanosome with a rigid skeleton of fused quadriradiate spicules cemented together, or formed by intertwined rays of the triradiate and quadriradiate spicules at the base of the sponge; free spicules may include tri- and quadriradiates, monactinal or diactinal and tuning fork spicules, some or all of in the ectosomal skeleton; subgastral sagittal radiates apparently absent; nuclei of choanocytes are apical; larvae are amphiblastula; canal system in all known forms is leuconoid.

Scope: Five extant genera are recognised.

Reviews: Hartman (1958), Vacelet (1970, 1981), Brien et al. (1973), Hartman (1980).

Genera:
Petrostoma Döderlein, 1892 (type species: Petrostoma schulzei Döderlein, 1892) - digitate processes arising from a common base; surface even, texture hard; oscules not obvious; subregular to sagittal quadriradiates of the chamber layer fused together laterally by calcareous cement into a network; ectosomal skeleton of separate quadriradiates and triradiates and bunches of tuning-fork spicules (Burton, 1963).
Minchinella Kirkpatrick, 1908 (type species: Minchinella lamellosa Kirkpatrick, 1908) - flabellate; even surface, minutely hispid; oscules papillate, pores on fistular processes; texture hard; main skeleton of fused quadriradiates; ectosomal skeleton a palisade of microxeas, with microxeas of several sizes, triradiates and quadriradiates with paired rays, and tuning-fork spicules in pore and ocular processes (Burton, 1963).
Monoplectroninia Pouliquen & Vacelet, 1970 (type species: Monoplectroninia hispida Pouliquen & Vacelet, 1970) - choanosomal skeleton composed of a basal layer made of one category of small tetractines cemented together by their basal actines, while their apical actine remains free and pointed. Cortical skeleton composed of free spicules (Borojevic, Boury-Esnault & Vacelet, in prep.).
Plectroninia Hinde, 1900 (type species: Plectroninia halli Hinde, 1900 [fossil form]) - quadriradiates of the main skeleton with their facial rays truncated or expanded terminally and fused at the end with facial rays of adjacent spicules, while the apical rays remain free and pointed; ectosomal skeleton of separate radiates, including tuning fork spicules and oxeas (Burton, 1963); P. hindei Kirkpatrick - encrusting; surface even, granular, oscules not seen; texture hard; main skeleton of fused quadriradiates, with a basal layer of sagittal triradiates, and with irregular triradiates, spined microxeas, tuning-fork spicules, spined pin-shaped spicules (Burton, 1963).
Tulearinia Vacelet, 1977 (type species: Tulearinia stylifera Vacelet, 1977) - encrusting; hispid surface; ectosomal skeleton with long styliform diactines both tangential to and erect on the basal skeleton; large sagittal triactines form a cortex laying parallel to the surface; within the choanosome are also numerous microdiactines; basal skeleton composed of fused tetractines having basal actines bound together by interlamellar cement without suture, and the beds under the rays of triactines have the same form of union (Vacelet, 1977).