Scientists say they've located the oldest animal-built reef on Earth among the dry, land-locked sands of Namibia, evidence of the first animals to barricade themselves behind hard, protective shells.

It's often said that technology mimics nature, but nearly as often, nature mimics nature. Such was the case 550 million years ago, scientists say, when coral-like creatures called Cloudina banded together to build their own version of a reef -- the long deposits of sand and eroded rock that form beneath the ocean surface.

The ancient creatures affixed themselves to natural surfaces, and also to each other, by excreting a natural cement made of calcium carbonate. Like cement, the wet substance hardened to create an outer shell and protective barrier -- a buffer against the dangerous underwater world.

"It's like a series of hollow ice-cream cones all stacked up," said Rachel Wood, a professor at the University of Edinburgh in Scotland. "It might have been related to corals and anemones and jellyfish."

Now, those once useful reefs are eroding remnants of the Ediacaran Period in a region of southern Namibia littered with ancient fossils and sediment millions of years old.

In the recent study of Cloudina and these ancient reefs -- published this week in the journal Science -- researchers suggest the emergence of shells and hard structures, through the process known as biomineralization, signaled the end the Ediacaran Period and the beginning of increasing biodiversity during the Precambrian period.

"We have found that animals were building reefs even before the evolution of complex animal life, suggesting that there must have been selective pressures in the Precambrian Period that we have yet to understand," explained study author Wood.