Neoproterozoic. The Neoproterozoic Era is the unit of geologic time from 1,000 to 541 million years ago.[1] The terminal Era of the formal Proterozoic Eon (or the informal "Precambrian"), it is further subdivided into the Tonian, Cryogenian, and Ediacaran Periods.
The most severe glaciation known in the geologic record occurred during the Cryogenian, when ice sheets reached the equator and formed a possible "Snowball Earth". The earliest fossils of multicellular life are found in the Ediacaran, including the earliest animals.
Cryogenian period. Ediacaran period. Precambrian. Positions of landmasses near the end of the Precambrian Overview[edit] Relatively little is known about the Precambrian, despite its making up roughly seven-eighths of the Earth's history, and what is known has largely been discovered in the past 50 years.
The Precambrian fossil record is poorer than that of the succeeding Phanerozoic, and those fossils present (e.g. stromatolites) are of limited biostratigraphic use.[1] This is because many Precambrian rocks are heavily metamorphosed, obscuring their origins, while others have either been destroyed by erosion, or remain deeply buried beneath Phanerozoic strata.[1][2] It is thought that the Earth itself coalesced from material in orbit around the Sun roughly 4500 Ma, or 4.5 billion years ago (Ga), and may have been struck by a very large (Mars-sized) planetesimal shortly after it formed, splitting off material that came together to form the Moon (see Giant impact hypothesis).