High Quality Content by WIKIPEDIA articles! 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.