Geologic Time Scale: Precambrian
(4.5 billion years ago to 538.8 million years ago)
The Precambrian or Cryptozoic is the earliest part of Earth’s history, set before the current Phanerozoic Eon. The Precambrian is named because it preceded the Cambrian, which itself is named after Cambria, the Latinised name for Wales, where rocks from this age were first studied. The Precambrian accounts for 88% of Earth’s geologic time.
Neoproterozic (Ediacaran): 635.0 to 538.8 million years ago
The Proterozoic (2,500 to 538.8 million years ago) is the most recent part of the Precambrian “super eon”. It is also the longest eon of the Earth’s geologic time scale.
Neoproterozoic Era (1,000 to 538.8 million years ago), was the last era of the Precambrian Supereon and the Proterozoic Eon; it is subdivided into the Tonian, Cryogenian, and Ediacaran periods.
The Ediacaran Period is named after the Ediacara Hill of South Australia and marks the end of the Proterozoic Eon. The Ediacaran was ratified in 2004 by the International Union of Geological Sciences (IUGS) and is followed by the Cambrian Period of the Phanerozoic Eron. The Ediacaran is known for the first appearance of widespread multicellular fauna (Ediacaran biota) following the of Snowball Earth glaciation events.