The calcareoussponges are members of the animal phylum Porifera, the cellular sponges. They are characterized by spicules made of calcium carbonate, in the form of high-magnesium calcite or aragonite. While the spicules in most species are triradiate, some species may possess two- or four-pointed spicules. Unlike other sponges, calcareans lack microscleres, tiny spicules which reinforce the flesh. In addition, their spicules develop from the outside-in, mineralizing within a hollow organic sheath.
Leucosolenida is an order of sponges in the class Calcarea and the subclass Calcaronea. Species in the order Leucosolenida are calcareous, with a skeleton composed exclusively of free spicules without calcified non-spicular reinforcements.
Demosponges (Demospongiae) are the most diverse class in the phylum Porifera. They include 76.2% of all species of sponges with nearly 8,800 species worldwide. They are sponges with a soft body that covers a hard, often massive skeleton made of calcium carbonate, either aragonite or calcite. They are predominantly leuconoid in structure. Their "skeletons" are made of spicules consisting of fibers of the protein spongin, the mineral silica, or both. Where spicules of silica are present, they have a different shape from those in the otherwise similar glass sponges. Some species, in particular from the Antarctic, obtain the silica for spicule building from the ingestion of siliceous diatoms.
Minchinellidae is a family of calcareous sponges, members of the class Calcarea. It is the only family in the monotypic order Lithonida. The families Petrobionidae and Lepidoleuconidae have also sometimes been placed within Lithonida, though more recently they have been moved to the order Baerida. Thanks to their hypercalcified structure, minchinellids have a fossil record reaching as far back as the Jurassic Period.
Baerida is an order of sea sponges in the subclass of Calcaronea, first described in 2000 by Radovan Borojevic, Nicole Boury-Esnault and Jean Vacelet. Baerida contains four families; two of these families were formerly placed within the order Lithonida.
Hexasterophora are a subclass of glass sponges in the class Hexactinellida. Most living hexasterophorans can be divided into three orders: Lyssacinosida, Lychniscosida, and Sceptrulophora. Like other glass sponges, hexasterophorans have skeletons composed of overlapping six-rayed spicules. In addition, they can be characterized by the presence of hexasters, a type of microsclere with six rays unfurling into multi-branched structures.
Chondrocladia is a genus of carnivorous demosponges of the family Cladorhizidae. Neocladia was long considered a junior synonym, but has recently become accepted as a distinct genus.
Homosclerophorida is an order of marine sponges. It is the only order in the monotypic class Homoscleromorpha. The order is composed of two families: Plakinidae and Oscarellidae.
Lyssacinosida is an order of glass sponges (Hexactinellida) belonging to the subclass Hexasterophora. These sponges can be recognized by their parenchymal spicules usually being unconnected, unlike in other sponges in the subclass where the spicules form a more or less tightly connected skeleton. Lyssacine sponges have existed since the Upper Ordovician, and three families are still alive today. The Venus' flower basket is one of the most well-known and culturally significant of the glass sponges.
Spicules are structural elements found in most sponges. The meshing of many spicules serves as the sponge's skeleton and thus it provides structural support and potentially defense against predators.
Ascute asconoides is a species of calcareous sponge found in Australia.
Ascute uteoides is a species of calcareous sponge found in Australia.
Homaxinella is a genus of sea sponges in the family Suberitidae. The type species is Homaxinella balfourensis.
Reticulosa is an extinct order of sea sponges in the class Hexactinellida and the subclass Amphidiscophora. Reticulosans were diverse in shape and size, similar to their modern relatives, the amphidiscosidans. Some were smooth and attached to a surface at a flat point, others were polyhedral or ornamented with nodes, many were covered in bristles, and a few were even suspended above the seabed by a rope-like anchor of braided glass spicules.
Heteractinida is an extinct grade of Paleozoic (Cambrian–Permian) sponges, sometimes used as a class or order. They are most commonly considered paraphyletic with respect to Calcarea, though some studies instead argue that they are paraphyletic relative to Hexactinellida. Heteractinids can be distinguished by their six-pronged (snowflake-shaped) spicules, whose symmetry historically suggested a relationship with the triradial calcarean sponges.
Amphidiscosida is an order of hexactinellids. The Amphidiscosida are commonly regarded as the only living sponges in the subclass Amphidiscophora.
Soleneiscus is a genus of calcareous sponges in the family Dendyidae.
Leuclathrina is a genus of sponges belonging to the family Dendyidae. Species are found in the northeast Atlantic and in the Indian Ocean.
Sphaerocoeliidae is an extinct family of calcareous sponges, the only family in the monotypic order Sphaerocoeliida. Sphaerocoeliids are one of several unrelated sponge groups described as "sphinctozoans", with a distinctive multi-chambered body structure. Sphaerocoeliids persisted from the Permian to the Cenomanian stage of the Cretaceous, a longer period of time than most other "sphinctozoans". Sphaerocoeliids make up the majority of calcareous "sphinctozoans", as well as a large portion of post-Triassic "sphinctozoan" diversity. "Sphinctozoans" and the similar "inozoans" were historically grouped together in the polyphyletic order Pharetronida.
Radiocyatha is an extinct group of sponge-like animals which lived in the early to mid-Cambrian Period.
