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Sponges constitute the phylum Porifera, and have been defined as sessile metazoans (multicelled immobile animals) that have water intake and outlet openings connected by chambers lined with choanocytes, cells with whip-like flagella. [13]: 29 However, a few carnivorous sponges have lost these water flow systems and the choanocytes.
Demosponges (Demospongiae) are the most diverse class in the phylum Porifera. They include greater than 90% of all species of sponges with nearly 8,800 species worldwide (World Porifera Database). [5] They are sponges with a soft body that covers a hard, often massive skeleton made of calcium carbonate, either aragonite or calcite [citation ...
Some molecular analyses suggest the class Calcarea is not exclusively related to other sponges, and should thus be designated as a phylum. This would also render Porifera (the sponge phylum) paraphyletic. Borchiellini et al. (2001) argued that calcareans were more closely related to Eumetazoa (non-sponge animals) than to other sponges. [9]
But some invertebrate paleontologists have placed them in an extinct, separate phylum, known appropriately as the Archaeocyatha. [11] However, one cladistic analysis [12] suggests that Archaeocyatha is a clade nested within the phylum Porifera (better known as the true sponges). True archaeocyathans coexisted with other enigmatic sponge-like ...
Parazoa (Parazoa, gr. Παρα-, para, "next to", and ζωα, zoa, "animals") are a taxon with sub-kingdom category that is located at the base of the phylogenetic tree of the animal kingdom in opposition to the sub-kingdom Eumetazoa; they group together the most primitive forms, characterized by not having proper tissues or that, in any case, these tissues are only partially differentiated.
They are usually classified along with other sponges in the phylum Porifera, but some researchers consider them sufficiently distinct to deserve their own phylum, Symplasma. Some experts believe glass sponges are the longest-lived animals on earth; [2] these scientists tentatively estimate a maximum age of up to 15,000 years.
Spongilla is a genus of freshwater sponges containing over 200 different species. Spongilla was first publicly recognized in 1696 by Leonard Plukenet and can be found in lakes, ponds and slow streams. [2]
The definition was posited because extinct organisms are hardest to classify: they can be offshoots that diverged from a phylum's line before the characters that define the modern phylum were all acquired. By Budd and Jensen's definition, a phylum is defined by a set of characters shared by all its living representatives.