The Garden of the Ediacaran was a period in the ancient past when Earth’s shallow seas were populated with a bewildering variety of enigmatic, soft-bodied creatures. Scientists have pictured it as a tranquil, almost idyllic interlude that lasted from 635 to 540 million years ago. But a new interdisciplinary study suggests that the organisms living at the time may have been much more dynamic than experts have thought.
Scientists have found It extremely difficult to fit these Precambrian species into the tree of life. That is because they lived in a time before organisms developed the ability to make shells or bones. As a result, they didn’t leave much fossil evidence of their existence behind, and even less evidence that they moved around. So, experts have generally concluded that virtually all of the Ediacarans — with the possible exception of a few organisms similar to jellyfish that floated about — were stationary and lived out their adult lives fixed in one place on the sea floor.
The new findings concern one of the most enigmatic of the Ediacaran genera, a penny-sized organism called Parvancorina, which is characterized by a series of ridges on its back that form the shape of a tiny anchor. By analyzing the way in which water flows around Parvancorina’s body, an international team of researchers has concluded that these ancient creatures must have been mobile: specifically, they must have had the ability to orient themselves to face into the current flowing around them. That would make them the oldest species known to possess this capability, which scientists call rheotaxis. Paper. (paywall) – Simon A. F. Darroch, Imran A. Rahman, Brandt Gibson, Rachel A. Racicot, Marc Laflamme. Inference of facultative mobility in the enigmatic Ediacaran organism Parvancorina. Biology Letters, 2017; 13 (5): 20170033 DOI: 10.1098/rsbl.2017.0033 More.
635 to 540 million years ago? So much for the long, slow period of development of these characteristics.
See also: Animal with muscles found from 560 mya (Ediacaran period)
Researchers: Life at 3.48 bya found in fresh water, not salt water
Stasis: Life goes on but evolution does not happen
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