Heteroscleromorpha has the most taxa of the demosponge subclasses, with an estimated 7500 species.
Its origin can be traced back to the Cambrian period, with the oldest fossil found in Sirius Passet, Greenland. But the true origin of the group may be even older.[4]
References
↑Cárdenas, P.; Pérez, T.; Boury-Esnault, N. (2012). Sponge Systematics Facing New Challenges. Advances in Sponge Science: Phylogeny, Systematics, Ecology. 79-209., page(s): 170
↑van Soest, R. (2016). Heteroscleromorpha. Accessed through World Register of Marine Species on 2017-02-17.
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