AsianScientist (Mar. 12, 2012) – The oldest animal with a skeleton has been discovered in South Australia by a team of paleontologists. The organism, called Coronacollina acula, is shaped like a thimble to which at least four 20 to 40 centimeter long needle-like “spicules” are attached.
Translated directly to “little rimmed hill with needles,” Coronacollina acula may have been three to five centimeters tall. It is constructed in the same way as Cambrian sponges, and researchers believe it ingested food in the same manner. How it reproduced remains a mystery.
The fossil of the animal is dated at 560 to 550 million years old, which places it in the Ediacaran period, before the explosion of life and diversification of organisms took place on Earth in the Cambrian.
The team’s findings provide insight into the evolution of life – particularly, early life – on the planet, why animals go extinct, and how organisms respond to environmental changes.
“Up until the Cambrian, it was understood that animals were soft bodied and had no hard parts,” said senior author Mary Droser, a professor of geology at the University of California, Riverside.
“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 – they would have been structural supports – essentially holding it up. This is a major innovation for animals,” she said.
According to Droser, the appearance of Coronacollina acula signals that the initiation of skeletons was not as sudden in the Cambrian as was thought, and that Ediacaran animals like it are part of the evolutionary lineage of animals as we know them.
“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,” she said.
The article can be found at: Clites EC et al. (2012) The advent of hard-part structural support among the Ediacara biota: Ediacaran harbinger of a Cambrian mode of body construction.
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Source: University of California -Riverside; Photo: Daniel Garson for Droser lab, UC Riverside.
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