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The increase in diversity of lifeforms during the early Cambrian is called the Cambrian explosion of life. [30] [31] While land seems to have been devoid of plants and animals, cyanobacteria and other microbes formed prokaryotic mats that covered terrestrial areas. [32]
The Precambrian dates from around 3850 to 542 million years ago. The Neoproterozoic is characterized by a large glaciation event, followed by the appearance of the first multicellular body plans before the Cambrian Explosion. Until the late 1950s, the Precambrian was not believed to have hosted multicellular organisms.
The Avalon explosion, named from the Precambrian faunal trace fossils discovered on the Avalon Peninsula in Newfoundland, eastern Canada, is a proposed evolutionary radiation of prehistoric animals about 575 million years ago in the Ediacaran period, with the Avalon explosion being one of three eras grouped in this time period. [3]
Great changes were happening at the end of the Precambrian and the start of the Early Cambrian. The breakup of the supercontinents , [ 140 ] rising sea levels (creating shallow, "life-friendly" seas), [ 141 ] a nutrient crisis, [ 142 ] fluctuations in atmospheric composition, including oxygen and carbon dioxide levels, [ 143 ] and changes in ...
This contrasts with the Ediacaran and early Cambrian periods, in which the quantity and variety of speciations, changes, and extinctions exploded. [ 26 ] Classically, the boundary between the Proterozoic and the Phanerozoic eons was set at the base of the Cambrian Period when the first fossils of animals, including trilobites and archeocyathids ...
Acceptance of Charnia as a Precambrian lifeform resulted in recognition of other major Precambrian animal groups, although the sea pen interpretation of Charnia has been recently discredited, [20] [21] and the current [needs update] "state of the art" is something of a "statement of ignorance". [22]
In the early 20th century, paleontologists started finding fossils of multicellular animals that predated the Cambrian. A complex fauna was found in South West Africa in the 1920s but was inaccurately dated. Another fauna was found in South Australia in the 1940s, but it was not thoroughly examined until the late 1950s.
List of extinct animals of Romania; List of fossil species in the La Brea Tar Pits, California, United States; List of fossil species in the London Clay, England; List of White Sea biota species by phylum, Russia; Paleobiota of the Hell Creek Formation, northern United States; Paleobiota of the Morrison Formation, western United States