Dawn of Animal Life
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Ediacara Biota - Ancestors of Modern Life or Evolutionary Dead End?
In 1946, our view of ancient life was changed dramatically when the first convincing fossils of Precambrian animals were found in the Ediacara Hills of Australia. The unusual fossils, originally interpreted as jellyfish, strange worms, and frond-like corals, gave scientists their first look at the animals that populated the Precambrian seas. The blue areas on the map show rocks of Ediacaran age, and the red dot shows the original discovery site in the Ediacara Hills.
Before this discovery, it was believed either that animals had not evolved during the Precambrian, or that they could not be fossilized since they did not have hard skeletons or shells. We now know that animals did evolve more than 545 million years ago, and that even though they were soft-bodied their body shapes were preserved during rapid burial by sand.
Since the discovery in Australia, the Ediacara Biota (named after the discovery site) has been found at more than 30 localities worldwide on every continent except Antarctica. As with any new discovery, scientists have differing opinions about the nature of the animals, and even if they were true animals. Some feel that they are the ancestors of modern animals, while others view them as a unique group that went totally extinct 545 million years ago.
The Edicaran of Canada
In Canada, Ediacaran fossils are found in the Northwest Territories, Yukon, British Columbia, and Newfoundland. The Mackenzie Mountains, NWT, has the thickest continuous section of rock (2.5 kilometres) containing Ediacaran fossils in the world. In addition to the myriad of disk-form fossils (like Ediacaria and Cyclomedusa), recent discoveries in Canadian rocks include the tentacled sea anemone-like creature Hiemalora, the segmented-form Windermeria, and the frond-like "spindles" of The Mistaken Point Fossil Assemblage of Newfoundland.
Cutting-edge research on Precambrian life is being done in Canada, notably at Queen's University and the University of Montreal. The mysteries of this important but obscure time in the development of life on Earth are being unravelled through careful study of Canadian fossils and others found around the world.
Recent fossils found in Namibia show us that members of the Ediacara Biota did populate the oceans up until the end of the Precambrian (545 million years ago). With the close of the Precambrian, much of the Ediacara Biota would become extinct. Many of them seem to be "failed experiments" in the evolution of life on Earth that became extinct just before the Cambrian "Explosion" of Life.
Other Precambrian fossils do appear to be from the ancestors of modern animals. It is generally agreed that simple burrows and trace-fossils (such as Helminthopsis pictured to the left) found in upper Precambrian rocks were made by primitive worms. These worms, and some other members of the Ediacara Biota, survived the extinction event and took part in the greatest evolutionary event in Earth's history: The Cambrian "Explosion" of Life. Within 35 million years of the end of the Precambrian, representatives of essentially all modern phyla were present in the Cambrian seas.