"If you were snorkeling over it nearly 550 million years ago, you'd see areas of green surface, from stromatolites, and then you'd see these little patches of tubes all growing together, forming a little thicket, or mound, on the seafloor," Wood said.
Cloudina likely formed reefs to protect itself from predators. In China, for instance, scientists have unearthed Cloudina fossils with holes drilled in them, likely from acid secreted by a predator animal, Wood said.
Clumping together on reefs would have also brought nutrient-rich currents close to the filter feeders at a time when more life forms were competing for space and food, the authors said.
"All together it paints a picture of quite significant ecological complexity," Wood said.
The fossils were described today (June 26) in the journal Science.
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