Sponges are one of the very oldest branches of the animal family tree, originating sometime in the Proterozoic Eon. Fossils are known from at least 600 million years ago, and their ancestry probably goes back even further back than that into the Cryogenian Period or late Tonian Period, at least 750 million years ago.
So it’s not especially surprising that sponges were already common and highly diverse in the Cambrian, with representatives of the major modern groups all present – demosponges, glass sponges, and calcareous sponges.
Continue reading “Cambrian Explosion Month #02: Phylum Porifera”