Scientists said this weekend that they've found the oldest animal-built reef on Earth among the land-locked sands of Namibia.

Tiny creatures created the reef some 548 million years ago, and the ancient structure is the oldest-known feature of its kind to be discovered, according to a press release by the University of Edinburgh.

The structure is 18 million years older than any other in the world. It was created by Cloudina, filter-feeders that were the first known life form to possess hard shells.

Researchers believe that the ancient animals were first to develop the ability to form shells and create reefs, according to the release.

The discovery revealed changes to scientists that were happening in life forms millions of years before the Cambrian explosion 542 million years ago.

Cloudina affixed themselves to surfaces, and to each other, by excreting a natural cement made of calcium carbonate, according to the release.

The wet substance then hardened to create an outer shell and protective barrier.

"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, according to the release. "It might have been related to corals and anemones and jellyfish."

The study of the reef was published in the journal Science recently.

In the study, researchers said that the emergence of shells and hard structures meant the end of 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," said Wood, the author of the study.

The work was supported by the Natural Environment Research Council, the University of Edinburgh and the Laidlaw Trust.

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