Australia: The Land Where Time Began

A biography of the Australian continent 

About 635-610 million years ago to 542 million years ago (the precise time of the beginning of the Ediacaran Era is still being refined, the end of the era is the beginning of the next era, the Palaeozoic). The boundary between the Ediacaran and the following Precambrian is clearly marked in the Flinders Ranges. Beneath the boundary all the fossils found have no hard parts, such as shells or scales, and signs of movement are restricted to the surface of the sea bed and the surface of algal mats or bacterial mats. Above the boundary, hard coverings such as shells, scales and armour plating are present and they are burrowing into the sea floor. It has been suggested that the appearance of armour may have been a reaction to the first appearance of predators. This has also been suggested as a driving force for some animals to start burrowing to escape predation. Once under the surface a new feeding niche would be available, eating buried nutrients such as dead animals. The addition of hard outer coverings would also provide attachment sites for muscles that could then be used more effectively in movement.

Australia was part of Gondwana and situated at the equator between about 542 and 510 million years ago. At this time some of the archaeocyathids built large barrier reefs, indicating the water was warmer than it had been previously.

The area of the Flinders Ranges was no longer covered by the sea by the Middle Cambrian

The Ediacaran Era is the oldest Era of life in the Proterozoic Eon. Until the announcement of its definition in 2004 the succeeding Palaeozoic Era was the oldest defined subdivision of the Phanerozoic Eon. The Era preceding the Ediacaran, sometimes known as the Cryogenian, because of extensive glaciation of the Earth at that time, is still not sufficiently defined to be officially named. This time has been called Snowball Earth, because most, if not all of the surface of the Earth, is believed to have been gripped in a severe glacial phase.

The Era was named for the type location, the Ediacara Hills, in the Flinders Ranges of South Australia. This was the site of discovery of a number of relatively large, soft bodied animals that are believed to be the earliest known representatives of successful multicellular animals. Other sites with a similar fauna have since been found in other parts of the world which are from a similar period in evolution, and are of a similar age.

During this era the fossils that were forming were almost all, though not entirely soft-bodied organisms with no hard parts, the few animals with hard parts were mostly small. There were a variety of fossils known as small shelly fossils, and forms such as Cloudina and Namacalatus. It has been suggested that crystallising of Namacalatus may have occurred after deposition (Fedonkin et al., 2007). Animals with hard parts became widespread in the following Cambrian, the Cambrian Explosion. It appears hard parts weren't present on large animals from this time.

In this era the bodies of soft bodied animals were preserved in sandstone and claystone, and it has been suggested that the bodies could have been fossilised with the aid of resistant material such as cellulose (Vickers-Rich, 2006). The only known animals that are capable of incorporating cellulose fibres into their bodies are tunicates, but it has been suggested they may have gained the ability to synthesise cellulose by horizontal gene transfer (Nakashima et al., 2004).

Sources & Further reading

• Mikhail A. Fedonkin, James G. Gehling, Kathleen Grey, Guy M. Narbonne, Patricia Vickers-Rich, The Rise of Animals, Evolution and Diversification of the Kingdom Animalia, Johns Hopkins University Press, Baltimore, 2007
• Penny Van Oosterzee, The Centre - The Natural history of Australia's Desert Regions, Reed Australia, 1993
• Mary E. White, The Nature of Hidden Worlds, Reed, 1993

Links

• Ediacaran Era
• Ediacaran Hills
• Ediacaran Fauna
• Ediacaran Fauna Distribution
• Ediacaran Fauna Distribution by Country
• Ediacaran Fauna Taxonomy
• Ediacaran Species
• Australian Age of Dinosaurs