Eight-armed animals colonized world's oceans before dinosaurs

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Washington, Oct 31 : A new study has suggested that an eight-armed creature colonized a large section of the world's oceans over 300 million years before the first dinosaurs emerged.

According to a report in Discovery News, the findings represent the first comparable animal fossils from the Ediacaran Period, 635 to 541 million years ago, which appear in two drastically different preservation environments - black shale of South China and quartz rock of South Australia.

"According to paleogeographic reconstructions, South China and South Australia were close to each other at the time, belonging to a supercontinent called Gondwana," said lead author Maoyan Zhu.

Zhu, Gehling and their colleagues collected eight compressions of the animals from the Doushantuo Formation at Wenghui, China.

They then traveled to Flinders Ranges, Australia, and collected seven specimens, leaving 31 others on two excavated and reassembled beds.

There is no question that the creature, called Eoandromeda octobrachiata, believed to represent one type of animal, had a lot of arms.

"The eight arms are clearly preserved in our specimens," Zhu said, adding that the arms were tubular and in close contact with each other, but not joined.

He and his colleagues believe the animal was a soft-bodied, dome-shaped organism that lived on seabeds and fed by absorbing dissolved nutrients from the ambient environment.

Before the latest fossils were found, some researchers identified the creatures as lichens or fungus-like organisms, but Zhu and his team suspect that at least some Ediacara fossils represent now-extinct diploblastic animals, or creatures that possess only two cellular layers separated by a jelly-type substance.

"Diploblastic animals are common creatures on present day Earth," he said, mentioning that jellyfish, corals and sea anemones belong to the group.

"These animals display radial symmetry, but lack complex organs, as shown by E. octobrachiata," he added.

The multi-armed creature, and several other early life forms, went extinct around 542 million years ago, which Zhu said, "left empty niches for the subsequent Cambrian explosion of complex animals."

Representatives of nearly all existent animals emerged at this time, when a rapid increase in oxygen made respiration and metabolism possible.

ANI

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