標題: Oldest animal with a skeleton discovered 560 million years old [打印本頁] 作者:
fossilshk 時間: 2012-3-13 02:10 AM 標題: Oldest animal with a skeleton discovered 560 million years old
Oldest animal with a skeleton discovered: It's 560 million years old and provides a crucial insight into the evolution of life
At between 550 and 560 million years old, an animal discovered in South Australia recently is the oldest with a skeleton ever found.
The organism, called Coronacollina acula, was found by a team from the University of California.
The finding provides insight into the evolution of life – particularly, early life – on the planet, why animals go extinct, and how organisms respond to environmental changes.
Rock on: These are the best Coronacollina specimens showing the main body with articulated spicules
The discovery also can help scientists recognise life elsewhere in the universe.
Coronacollina acula lived on the seafloor. It was shaped like a thimble with at least four 20 to 40-centimetre-long spikes called ’spicules’ attached. These probably held the creature up.
The researchers believe it ingested food in the same manner a sponge does, and that it was incapable of moving around. How it reproduced remains a mystery.
How Coronacollina would have appeared in life: It remained in place on the sea floor and may have used its spicules as support struts
Its age places it in the Ediacaran period, before the explosion of life and diversification of organisms took place on Earth in the Cambrian, 488 to 542 million years ago.
‘Up until the Cambrian, it was understood that animals were soft bodied and had no hard parts,’ said Mary Droser, lead researcher and a professor of geology at the University of California.
‘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.’
Coronacollina acula is seen in the fossils as a depression measuring a few millimetres to two centimetres deep. But because rocks compact over time, the organism could have been bigger – three to five centimetres tall. Notably, it is constructed in the same way that Cambrian sponges were constructed.
‘It therefore provides a link between the two time intervals,’ Droser said. ‘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.’
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,’ she said. ‘Our discovery shows that they did not.’
Results of the study appeared online recently in Geology.
