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article imageOldest Pre-Cambrian organism with skeleton found in Australia

By JohnThomas Didymus     Mar 9, 2012 in Science
A team of paleontologists say they have discovered the oldest known animal with a skeleton. The animal is about 560 to 550 million years old. The scientists say the new find gives fresh insight into evolution of life before the Cambrian explosion.
The animal called Coronacollina acula, is from the Ediacaran geological period named after the Ediacara Hills of South Australia. The Ediacaran Period dates back about 630-542 million years. The animal Coronacollina acula is of special interest to paleontologists because the Ediacaran Period came before the famous Cambrian explosion (542-488 million years ago) which witnessed diversification of life forms. The new find extends the history of skeletal animals into the Pre-Cambrian era.
UCR Today reports Mary Droser, professor of geology at the University of California, Riverside, who led the team that discovered the new organism in South Australia, said: "Up until the Cambrian, it was understood that animals were soft bodied and had no hard parts. But we now have an organism with individual skeletal body parts that appears before the Cambrian. It is therefore the oldest animal with hard parts, and it has a number of them...This is a major innovation for animals."
Coronacollina acula is seen in the fossils as a depression measuring a few millimeters to 2 centimeters deep. But because rocks compact over time, the organism could have been bigger, about 3 to 5 centimeters tall. The scientists point out the animal is similar to Cambrian sponges in construction. Droser comments: "It therefore provides a link between the two time intervals. We're calling it the 'harbinger of Cambrian constructional morphology,' which is to say it's a precursor of organisms seen in the Cambrian. This is tremendously exciting because it is the first appearance of one of the major novelties of animal evolution."
Science Daily reports Droser said the find shows that the so-called Cambrian explosion was not as dramatic is often imagined. UCR Today reports Droser said the appearance of the animal marks the beginning of evolution of skeletal animals and that Ediacaran organisms fill in some of the gaps in the evolutionary lineage.
 The best Coronacollina specimens showing the main body with articulated spicules. Specimens origina...
"The best Coronacollina specimens showing the main body with articulated spicules. Specimens originate from different field localities. Arrows indicate main body of Coronacollina. White bars indicate 1 cm. A, C, D and E are photographs of fossil impressions in the rock. B and F are latex casts showing how the fossils would have looked in life, after compression."
Droser lab, UC Riverside.
A reconstruction of how Coronacollina would have appeared in life
A reconstruction of how Coronacollina would have appeared in life
Daniel Garson, Droser lab, UC Riverside.
The palaeontologist said:"The fate of the earliest Ediacaran animals has been a subject of debate, with many suggesting that they all went extinct just before the Cambrian. Our discovery shows that they did not."
According to the researchers, the animal lived on the seafloor. It was shaped like a thimble to which was attached about four "20-40-centimeter-long needle-like spicules." The researchers believe the animal held itself up by its spicules and fed in the same manner as sponges, but it was not able to move about. Nothing is known about how the animal reproduced.
UCR Today reports the name Coronacollina acula translates "little rimmed hill with needles," and is a reference to the animal's morphology which includes a truncated cone-shaped body and long brittle spicules, both of which appear in fossils as a pit and thin grooves respectively.
According to Droser, the organism appears to have been gregarious: "We've now found whole organisms of Coronacollina acula, the thimble-shaped body in the center with spicules coming off it like knitting needles. And we have found hundreds of them. They appear to have been a gregarious species, with a lot of them living together."
Droser commented further on the significance of discovery of a Pre-Cambrian animal with a skeleton: "We often associate skeletons with predation since skeletons greatly assist animals in their fight against predators. But Coronacollina acula used its skeleton only for support, there being no predators in the Ediacaran."
More about ediacaran period, Coronacollina acula, South australia
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