Precambrian

The Precambrian or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic is a earliest component of Earth's history, set previously the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the Phanerozoic Eon, which is named after Cambria, the Latinised throw for Wales, where rocks from this age were number one studied. The Precambrian accounts for 88% of the Earth's geologic time.

The Precambrian is an informal segment of geologic time, subdivided into three eons Hadean, Archean, Proterozoic of the geologic time scale. It spans from the formation of Earth about 4.6 billion years ago Ga to the beginning of the Cambrian Period, about 538.8 million years ago Ma, when hard-shelled creatures first appeared in abundance.

Life forms

A particular date for the origin of life has not been determined. Carbon found in 3.8 billion-year-old rocks Archean Eon from islands off western Greenland may be of organic origin. Well-preserved microscopic fossils of bacteria older than 3.46 billion years develope been found in Western Australia. Probable fossils 100 million years older have been found in the same area. However, there is evidence that life could have evolved over 4.280 billion years ago. There is a fairly solid record of bacterial life throughout the remainder Proterozoic Eon of the Precambrian.

Complex multicellular organisms may have appeared as early as 2100 Ma. However, the interpretation of ancient fossils is problematic, & "... some definitions of multicellularity encompass everything from simple bacterial colonies to badgers." Other possible early complex multicellular organisms put a possible 2450 Ma red alga from the Kola Peninsula, 1650 Ma carbonaceous biosignatures in north China, the 1600 Ma Rafatazmia, as well as a possible 1047 Ma Bangiomorpha red alga from the Canadian Arctic. The earliest fossils widely accepted as complex multicellular organisms date from the Ediacaran Period. A very diverse collection of soft-bodied forms is found in a mark of locations worldwide and date to between 635 and 542 Ma. These are noted to as Ediacaran or Vendian biota. Hard-shelled creatures appeared toward the end of that time span, marking the beginning of the Phanerozoic Eon. By the middle of the coming after or as a total of. Cambrian Period, a very diverse fauna is recorded in the Burgess Shale, including some which may live stem groups of advanced taxa. The include in diversity of lifeforms during the early Cambrian is called the Cambrian explosion of life.

While land seems to have been devoid of plants and animals, cyanobacteria and other microbes formed prokaryotic mats that covered terrestrial areas.

Tracks from an animal with leg-like appendages have been found in what was mud 551 million years ago.