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'''Calcarea''' is a class of the animal phylum [[Porifera]], consisting of calcareous sponges, characterized by 2-4 spicules made of [[calcium carbonate]] in the form of calcite or aragonite. There are about 400 species of sponges in the Calcarea group, exclusively [[marine]], found throughout the oceans, but mainly in temperate areas.  

'''Calcarea''' is a class of the animal phylum [[Porifera]], consisting of [[calcareous]] sponges, characterized by 2-4 spicules made of [[calcium carbonate]] in the form of calcite or aragonite. There are about 400 species of sponges in the Calcarea group, exclusively [[marine]], found throughout the oceans, but mainly in temperate areas.  

Calcarea sponges are usually found in shallower, sheltered waters less than 1000 m, and in tropical regions they are associated with coral reefs. Thought to be the most primitive group of sponges, it is the only class with [[asconoid]] and [[syconoid]] construction, and has sponges with [[leuconoid]] construction as well. The [[Hexactinellida]] and [[Demospongiae]] groups have only leuconoid forms. Calcarea is divided into two groups, '''Calcinea''' and '''Calcaronea''', differentiated by the larvae and location of the nuclei in the choanocytes. Calcinea is further divided to two orders and nine families, and Calcaronea has two orders and ten families. Taxonomic resolution is still being revised.<ref>Mulcrone, R. 2005. "Calcarea" [http://animaldiversity.ummz.umich.edu/site/accounts/information/Calcarea.html Animal Diversity Web] Accessed June 20, 2007</ref>

Calcarea sponges are usually found in shallower, sheltered waters less than 1000 m, and in tropical regions they are associated with coral reefs. Thought to be the most primitive group of sponges, it is the only class with [[asconoid]] and [[syconoid]] construction, and has sponges with [[leuconoid]] construction as well. The [[Hexactinellida]] and [[Demospongiae]] groups have only leuconoid forms. Calcarea is divided into two groups, '''Calcinea''' and '''Calcaronea''', differentiated by the larvae and location of the nuclei in the choanocytes. Calcinea is further divided to two orders and nine families, and Calcaronea has two orders and ten families. Taxonomic resolution is still being revised.<ref>Mulcrone, R. 2005. "Calcarea" [http://animaldiversity.ummz.umich.edu/site/accounts/information/Calcarea.html Animal Diversity Web] Accessed June 20, 2007</ref>