Schulze, 1880
Definition: Order Homosclerophorida. The only family of the order (following Diaz and Van Soest, 1994). It includes thinly to thickly encrusting sponges. The skeleton is formed by a combination of calthropses, which may or may not have lophate rays (then dubbed lophotriaene), and/or reduced derivate spicules (diods and triods). These are generally arranged uniformly in the body, and usually surrounding the aquiferous system in a very regular "aveolar" way. There is no developed ectosomal skeleton separate from that of the choanosome. Specialized spicules (candelabras, microrhabds, etc.) may be added to the basic spiculation. Loss of siliceous skeleton is found in one genus (Oscarella), but has recently been registered also in local population of the spicule-bearing genus Corticium , now elevated to generic rank: Pseudocorticium Boury-Esnault and Muricy. Large choanocyte chambers mostly eurypyllous and the group has a unique amphiblastula-like larva.
Remarks: There are 12 nominal genera in this family: Genera considered valid are: Plakina , Plakortis , Plakinastrella , Placinolopha , Corticium , and Oscarella . They occur mainly in warm waters.
Source: Diaz and Van Soest, 1994.
Genera represented in the area:
Plakina Schulze, 1880 (type species: Plakina monolopha Schulze, 1889) (syn. Plakoosa de Laubenfels, 1936b)—thinly or massively encrusting; spiculation of of diods, triods and calthrops, and with lophotriaenes having one, two, three or four lophate rays; eurypylous choanocyte chambers usually with a radial arrangement of chambers around a central excurrent canal; lophocalthrops highly concentrated at sponge surface (Diaz and van Soest, 1994).
Plakortis Schulze, 1880 (type species: Plakortis simplex Schulze, 1880) (syn. Roosa de Laubenfels, 1934)—thinly to massively encrusting; skeleton formed mainly by small diods with triods in varying abundance; deformed calthrops in some species and some with diactine-derived microscleres dispersed regularly throughout the mesohyl (Diaz and van Soest, 1994) (Plakortis angulospiculatus).
Oscarella Vosmaer, 1884 (type species: Halisarca lobularis Schmidt, 1862) (syn. Oscaria sensu Vosmaer,1880; Octavella Tuzet and Paris, 1963)—encrusting, lobulate smooth surface; no spicules, no fibres; choanocyte chambers eurypylous.
Species included:
Oscarella lobularis
Plakina monolopha
Plakortis simplex