The Ediacarian is the final period of the Neoprotozoic Era. It took place from 630 million to 550 million years ago. The Ediacarian saw the first development of complex multicellular animal life. This predates the Cambrian explosion by 80 million years. Sponges, jellyfish, and primitive arthropods all thrived during this period. Algae also thrived during this period. Scientists believe that multicellular life, which existed since the early Tonian one billion years ago would have diversified sooner but two massive ice ages between 850 million years and 630 million years ago prevented that from happening. In the previous period, known as the Cryogenian, the Earth experienced its worst glaciation ever, much worse than the Plio-Pleistocene glaciations. Some scientists even speculate that the entire planet was glaciated resulting in Snowball Earth. After the Cryogeneian, the diversification of animal life began. This was the Ediacarian.