Bowerbank, 1864
Definition: Exclusively marine Porifera in which the mineral skeleton is composed entirely of calcium carbonate. Skeletal elements (Calcarea spicules) are diactines (oxeas), triactines (triradiates) and tetractines (quadriradiates) (triactines/tetractines). Calcarea are always viviparous.
Remarks:
The Calcarea contains 2 subclasses, 5 orders, 18 families, 63 valid genera, and an estimated fauna of between 400-500 species worldwide. All species are marine.
The Calcarea have diverse bodyplans, two of which (asconoid organization and syconoid system) are unique for the Porifera.
The two subclasses are:
Subclass Calcinea Bidder, 1898
- Calcarea in which triactines and basal system of tetractines are regular (equiangular and equiradiate) or exceptionally inequi-angled (then called "parasagittal" or "sagittal"). In ontogeny, the first spicules to be secreted are triactines. Choanocytes are basinucleate (i.e. the nucleus is at the base of the cell) with spherical nuclei. The basal body of the flagellum is not adjacent to the nucleus. Calcinea have coeloblastula larvae.
Subclass Calcaronea Bidder, 1898
- Calcarea with the triactines and the basal system of tetractines inequi-angular (i.e. the angles of the rays are not equal, called "sagittal"), exceptionally regular. In ontogeny the first spicules to be secreted are diactines. Choanocytes are apinucleate (i.e. their nucleus is in the middle of the cell at the root (basal body) of the flagellum) . Calcaronea have amphiblastula larvae.
Source: Borojevic et al., unpublished