Tuesday, July 26, 2005

Ediacara Fauna

The above is a picture of a type of ediacaran fossil called a vendobiont.
From Geotimes:

Radiometrically dated between 551 and 538 million years old, the newly discovered vendobionts, preserved in a limestone matrix, have internal structures replaced by calcite spars, says Bing Shen, a graduate student at Virginia Tech and co-author of the paper, published in the July 11 Online Early Edition of the Proceedings of the National Academy of Sciences. The creatures have a unique body plan never before seen in living or extinct creatures, Shen says.

Shen and his colleagues plan to perform other analyses of the specimens, including some geochemical work. They will also return to the field in search of more Ediacara fossils in the previously overlooked carbonate rocks. "It is important to search more limestone for different fossil anatomies [and] ecologies," Shen says. What exactly the vendobionts were and how they lived is still a point of speculation.

Indeed, the team has several ideas about why the organisms went extinct during the Cambrian, including a change in the environment. Another possibility, they say, is that because the vendobionts were sedentary creatures — lying about on the seafloor — organisms that could burrow into and crawl across the ocean bottom may have disrupted the lifestyle of the vendobionts.