Ediacaran

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Dickinsonia costata, an Ediacaran organism of unknown affinity, with a quilted appearance.
Dickinsonia costata, an Ediacaran organism of unknown affinity, with a quilted appearance.
Ediacaran
650-544 mya
Era: Proterozoic
Preceded by Cryogenian
Followed by Cambrian

Contents

Introduction

The Ediacaran refers to the period in earth history from 650 to 542 million years ago. Many important events happened during the Ediacaran such as the end of the worldwide ice age known as "Snowball Earth" around 600 ma, the appearance of an enigmatic fauna around 610 ma called the Ediacaran biota, or the appearance of the first Bilaterian animal around 580 ma.

Important Evolutionary Events

  • The first appearance of large complex organisms
  • The first fossil Bilaterian animal Vernanimalcula guizhouena
  • The appearance of the Vendazoa
  • The evolution of the earliest animal with sight and eyes Bomakellia kelleri (Which helps to debunk the claims of intelligent design proponents that state that The eye is too complex too have evolved and that the eye appeared suddenly in the Cambrian.)
  • The evolution of the ediacaran biota around 610 million years ago to 542 million years ago.

Ediacaran Biota

Bomakellia kelleri was an 8 to 9.5 centimeter long Edicaran organism that lived in the ocean at what is now the shores of the White Sea of Russia. It has a long body lined with oval-shaped appendages, giving it a tri-lobed appearance, and has a rounded, vaguely triangular shield on one end (identified as a cephalon by some, a holdfast by others). B. kelleri may have been a early arthropod (C) Stanton F. Fink
Bomakellia kelleri was an 8 to 9.5 centimeter long Edicaran organism that lived in the ocean at what is now the shores of the White Sea of Russia. It has a long body lined with oval-shaped appendages, giving it a tri-lobed appearance, and has a rounded, vaguely triangular shield on one end (identified as a cephalon by some, a holdfast by others). B. kelleri may have been a early arthropod (C) Stanton F. Fink
The Ediacaran biota are an enigmatic set of Ediacaran fossils that have been found in strata dating back to 655 million years ago to 542 million years ago. The Ediacaran Biota appeared shortly after the worldwide Snowball earth ice age which occurred in the previous Cryogenian period and in the early Ediacaran period around 750 million years ago to 635 million years ago. The Ediacaran Biota mostly disappeared during the early Cambrian around 542 million years ago although the fossil evidence indicates that some Ediacaran organisms may have continued to survive into the Middle Cambrian around 500 million years ago. Many organisms in the Ediacaran Biota appear to be completely unrelated to modern animals although others (such as Kimberella which may have been an early mollusk and Bomakellia kelleri which may have been an ancestral arthropod which thrived in the following Cambrian period) may have given rise to some of the more modern species of animals that thrived in the Cambrian period. Classifying the Ediacaran Biota is extremely difficult and as a result have been classified in a number of ways such as being cnidarians ,Lichens ,ancestors of modern animals ,a totally new phylum or even as a new kingdom separate from modern animals. Many theories have been proposed to explain why the Ediacaran Biota went extinct such as the evolution of shelled predators which could have easily eaten the soft and shell-less Ediacaran Biota Although the Ediacaran organism Kimberella may have had a predatory life style which suggests that the Ediacaran Biota was already exposed to some predation ,sampling bias due to changing conditions in the environment which may have not favored preservation of the Ediacaran organisms ,Change in environmental conditions such as the breakup of the Ediacaran supercontinent pannotia at the beginning of the Cambrian and rising sea levels (creating shallow, "life-friendly" seas which were prevalent throughout the Cambrian) and finally Competition with the more advanced Cambrian animals may also have played a role in the extinction of the Ediacaran fauna.

Paleogeography

This is a map of the earth around 550 Million years ago showing the final stages of the formation of the prehistoric continent Gondwana.
This is a map of the earth around 550 Million years ago showing the final stages of the formation of the prehistoric continent Gondwana.

Before the start of the Ediacaran a supercontinent called Rodinia began to form around 1.3 billion years ago from the merger of three or four pre-existing continents during an event known as the Grenville Orogeny and began to brake up into three major continents West Gondwana, East Gondwana, and Laurasia around 750 million years ago during the Tonian and Cryogenian periods. Two of these continents West and East Gondwana merged together during the Neoproterozoic orogenic event known as the Pan-African Orogeny. Shortly after Rodina dissembled another super continent called Pannotia formed in the Ediacaran period, only to break apart in the following Cambrian period. In contrast with the later Cambrian, the climate was quite cool and the sea levels were quite deep compared to the shallow waters of the Cambrian.

References

see also

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