Genus Placospongia Gray, 1867

Diagnosis (modified from Rützler & Hooper 2000): encrusting or branched sponges, covered by smooth cortical plates separated by contractile grooves, where pores and oscules are located. Size ranges from small crusts (average 25 cm 2, 2 mm thick) to erect branches (36 cm high, 1.5 cm and more in diameter). The live color of the known species is variable. Skeletal structure radiated, with tylostyles tracts that rise from a lower layer of selenasters (basal in encrusting specimens or as a central axis in branched specimens) and reach the cortex, where they support the margins of the cortical plates. Megascleres are tylostyles that can be of two size classes; microscleres include selenasters of the cortex and basal layer (or central axis), and streptasters, spherasters, microrhabds, oxyasters, microspirasters, and microspherasters in the choanosome and the ectosome.