Homosclerophorida Dendy (Demospongiae, Homoscleromorpha) contains a single family Plakinidae Schulze (including Oscarellidae Lendenfeld and Corticiidae Vosmaer), with seven valid genera and about 60 valid species worldwide. Species live mainly in shallow waters but a few have been recorded from abyssal depths (up to 2460m). Species are often encrusting, lobate, but massive species are common in some genera (Plakortis, Plakinastrella); surface is usually smooth or microhispid and consistency varies from soft to carti- laginous. All genera possess flagellated exo- and endopinacocytes, a basement membrane lining both choanoderm and pinacoderm, oval to spherical choanocyte chambers with a sylleibid-like or leuconoid organization, and a unique incubated cinctoblastula-type larvae; spicules, when present, are peculiar tetractines (calthrops) and derivatives. Genera are distinguished mainly by four morphological char- acters: presence of a siliceous skeleton; presence of a cortex associated with a leuconoid aquiferous system and well-developed mesohyl or a sylleibid aquiferous system with poorly developed mesohyl and ectosome; number of spicule size classes; and presence and type of ramifications in the actines of calthrops (tetractinal spicules), with three distinct general morphologies recognized.
CITATION STYLE
Vacelet, J. (2002). Recent ‘Sphinctozoa’, Order Verticillitida, Family Verticillitidae Steinmann, 1882. In Systema Porifera (pp. 1097–1098). Springer US. https://doi.org/10.1007/978-1-4615-0747-5_113
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