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Sponges
Sponges are a group of invertebrates that includes glass sponges, demisponges, and calcareous sponges. There are about 10,000 species of sponges alive today. The articles listed below provide information about the characteristics, classification and evolution of sponges.
Evidence of Early Sponges Discovered in Oman
Scientists studying sedimentary rocks in south Oman have discovered high concentrations of steroids that they believe were produced by ancient, multicelluar animals. The team proposes that the fossilized steroids, which date back 635 million years, were produced by sponges, one of the most basic forms of animal life on Earth.