Wikipedia
Namapoikia
Namapoikia rietoogensis is among the earliest known animals to produce a calcareous (probably aragonite) skeleton. Known from the Ediacaran period, before the Cambrian explosion of calcifying animals, the organism grew up to a metre in diameter and resembles a colonial sponge or cnidarian. It was an encruster, filling vertical fissures in the reefs in which it originally grew.
The fossil was first found in the Omkyk Member from Rietoog in southern Namibia, in association with another calcifying fossil, Cloudina.