The discovery of Ediacaran fossils in the
Flinders Ranges, South Australia is one of the most significant scientific
findings made in recent history. The fossils reveal a community of animals
living on the seafloor some 600 million years ago.
Mawsonites spriggi
In 1946, a geologist, Reg Sprigg visited the Ediacara Hills in the Flinders Ranges. On the bases of sandstone slabs, he found disc-like impressions that looked like jellyfish. Further investigation led him to believe that these fossils were evidence of the oldest animal life on Earth. He published his findings in two papers in 1947 and 1949.
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Wave ripple wall
The processes by which Ediacaran fossils were preserved is of great curiosity to scientists because soft-bodied organisms would not normally fossilise. In the Flinders Ranges, the Ediacaran fossils are found on sandy seafloor beds that were deposited by storm action and strong ocean currents. The fossils are found in bands of quartzite which form the prominent ridges of the Flinders Ranges.
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Community Slab
Ediacaran animals show evidence of feeding, movement and reproduction, making them the first known complex life on Earth.
Evidence of movement
Most Ediacaran animals didn’t move and were fixed to the seafloor. However some trace fossils have been found in South Australia’s Ediacaran rocks that suggest some animals moved across the seafloor mat to feed. Kimberella is a possible ancestor of gastropods (sea snails), it excavated the seafloor mat to find its food. Kimberella crawled along on a muscular foot. Sets of paired scratch marks made by Kimberella provide evidence that Ediacaran animals could move.
Dickinsonia
Dickinsonia is one of the most common animals among the Ediacara biota of South Australia. Its feeding traces are shown by depressions in the seafloor. It is thought that Dickinsonia moved by either muscular action, like a worm or using cilia (microscopic bristles) like living comb jellies today. Dickinsonia would settle on a spot on the seafloor, secrete digestive juices and absorb nutrients from the seafloor.
Interpretation
Some of the fossils found in the Ediacaran biota, particularly Aborea look like plants. Aborea is a frond attached to the seafloor by a disc. Despite looking like a plant, it is believed to be similar to Sea pen animals that live today.
Key specimens from the Ediacara biota
Spriggina floundersi was the first animal with a head. It had a segmented body with a horse-shoe shaped head.
It grew like other arthropods and ranged from 3 to 5 centimetres in length.
Spriggina is a possible ancestor to shrimps, millipedes and centipedes.
Parvancorina minchami
Parvancorina is a small anchor-shaped fossil. It was a bug shaped animal, with a strong medial ridge and arc-shaped head. Parvancorina looks like other fossil arthropods that have been found in the Cambrian period.
Tribrachidium heraldicum
Tribrachidium is a disc with three bent fringed arms. It was a small, rounded three-armed spiral shaped animal.
Tribrachidium had an unusual body form with three planes of symmetry. Tribrachidium had a radius of up to 5cm and was about 5-10 mm high.
Palaeophragmodictya
reticulata
Palaeophragmodictya reticulata was one of the earliest complete sponges with a dome shaped mesh skeleton. Sponges have no muscles, nerve network or internal organs and are the simplest known animals on Earth.
Some of the most important palaeontology sites in the world are found in South Australia. The South Australian Museum is responsible for around 50,000 registered fossil specimens. Strengths of the collection include fossils of the Ediacaran biota, South Australian Cambrian invertebrates, Late Triassic plant fossils, Early Cretaceous Marine vertebrates and invertebrates including opalised fossils, Tertiary invertebrates and Tertiary and Pleistocene vertebrates.
For more information on Ediacaran Fossils of the Flinders Ranges
http://www.outreacheducation.sa.edu.au/programs/ediacaran-fossils-of-the-flinders-ranges/
