Sponges Temporal range: Ediacaran-present;[1] probable Cryogenian record,[2] 544 –0 Ma Pha. Proterozoic Archean Had.
A stove-pipe sponge
Scientific classification
Kingdom:	Animalia
Phylum:	Porifera Grant, 1836
Classes
Calcarea Demospongiae Hexactinellida Homoscleromorpha Extinct groups †Archaeocyatha †"Heteractinida" (paraphyletic) †Stromatoporoidea †Cribricyatha †Olgunidae (family) †Eocyathispongia[3] †Otavia[4]
Synonyms
Parazoa/Ahistozoa (sans Placozoa)[5]

Sponges or sea sponges are primarily marine invertebrates of the animal phylum Porifera^[6] (/pəˈrɪfərəˌ pɔː-/; meaning 'pore bearer').^[7] They are sessile filter feeders that are bound to the seabed, and are one of the most ancient members of macrobenthos, with many historical species being important reef-building organisms.

Sponges are multicellular organisms consisting of jelly-like mesohyl sandwiched between two thin layers of cells, and usually have tube-like bodies full of pores and channels that allow water to circulate through them. They have unspecialized cells that can transform into other types and that often migrate between the main cell layers and the mesohyl in the process. They do not have complex nervous,^[8] digestive or circulatory systems. Instead, most rely on maintaining a constant water flow through their bodies to obtain food and oxygen and to remove wastes, usually via flagella movements of the so-called "collar cells".

Sponges may be the sister group to all other animals, although the evidence for this relationship remains inconclusive.^{[9][10][11][12][13][14]} Fossil evidence of primitive sponges such as Otavia dates to as early as the Tonian period (around 800 Mya). The branch of zoology that studies sponges is spongiology.^[15]