structural:scholar_edition
Classes

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. Therefore, they have recently been recognized as the fourth class of sponges.

Sponges are divided into classes mainly according to the composition of their skeletons: These are arranged in evolutionary order as shown below in ascending order of their evolution from top to bottom: