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These sponges are massive or encrusting in form and have a very simple structure with very little variation in spicule form (all spicules tend to be very small). Reproduction is viviparous and the larva is an oval form known as an amphiblastula. This form is usual in calcareous sponges but is less common in other sponges.
Sponges were traditionally distributed in three classes: calcareous sponges (Calcarea), glass sponges (Hexactinellida) and demosponges (Demospongiae). However, studies have now shown that the Homoscleromorpha , a group thought to belong to the Demospongiae , has a genetic relationship well separated from other sponge classes.
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 ...
Hexactinellid sponges are sponges with a skeleton made of four- and/or six-pointed siliceous spicules, often referred to as glass sponges. 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 .
The calcareous sponges [2] [3] (class Calcarea) 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 (with three points in a single plane), some species may possess two ...
Sponges are physically very distinct from other animals, and were long thought to have diverged first, representing the oldest animal phylum and forming a sister clade to all other animals. [118] Despite their morphological dissimilarity with all other animals, genetic evidence suggests sponges may be more closely related to other animals than ...
The phylum Porifera includes the aquatic fauna sponges. Subcategories. ... Sponges and humans (2 C, 2 P) P. Prehistoric sponges (6 C, 4 P) T. Sponge taxa by rank (5 C)
Human taxonomy is the classification of the human species within zoological taxonomy. The systematic genus , Homo , is designed to include both anatomically modern humans and extinct varieties of archaic humans .