In the middle of the Australian outback along a mountain chain called the Flinders Ranges, researchers have discovered a 650 million year old reef that was once underwater. Researchers say the tiny fossils they've already found in the ancient reef may be the earliest examples of multicellular organisms ever found, and may answer questions about how animal life evolved. Researcher Malcolm Wallace explains that the
oldest-known animal fossils are 570 million years old. The reef in the Flinders Ranges is 80 million years older than that and was, he said, “the right age to capture the precursors to animals” [The Times].
The first fossils discovered in the reef appear to be sponge-like multicellular organisms that resemble tiny cauliflowers, measuring less than an inch in diameter, but Wallace cautions that the creatures haven't been thoroughly studied yet. The reef's discovery was announced at a meeting of the Geological Society of Australia this week.
Unlike the Great Barrier Reef, the Oodnaminta Reef – named after an old hut near by – is not made of coral. “This reef is much too old to be made of coral,” Professor Wallace said. “It was constructed by microbial organisms and other complex, chambered structures that have not been discovered before.” Coral was first formed 520 million years ago, more than 100 million years after the Oodnaminta was formed [The Times].
The Oodnaminta Reef formed during a very warm period in the Earth's history, which was sandwiched between two intensely cold eras, when scientists believe ice extended to the planet's equator. Researchers say the tiny organisms found in the reef may have gone on to survive
one of the most extreme ice ages in Earth history which ended about 580 million years ago, apparently leaving descendents in the later life-friendly Ediacaran. "It's consistent with the argument that evolution was going on despite the severe cold," said Professor Wallace [The Australian].
The Ediacaran saw an explosion of complex multicellular organisms, including creatures that resembled worms and sea anemones; the sponges could be the ancestors of those species. For more on the the strange critters that flourished in the Ediacaran, see the DISCOVER article "When Life Was Odd."