550 Million-year-old coral reef formed by the first vertebrates discovered on the plains of Namibia
Scientists have reported that an ancient coral-like reef that formed in a primeval shallow sea nearly 550 million years ago has been discovered on what is now the dry scrubland of Namibia in southern Africa.
Scientists said that the reef was built over many years by long-extinct marine creatures which gradually created a reef similar to the way coral reefs are formed today.
According to the journal Science it’s the oldest known fossilised reef in the world. Dating techniques show that the reef was alive before the Cambrian Explosion about 542 million years ago, when multicellular life evolved rapidly into many diverse types, some of which are the ancestors of today’s main groups of animals, said Professor Rachel Wood of Edinburgh University, who led the study.
“It’s possible to date the reef from a layer of volcanic ash found just above it. Our best guess is that the reef was alive about 548 million years ago, which makes it the oldest to date, although something may still come out that is even older,” Professor Wood said.
The reef was made of filter-feeding marine animals called Cloudina which grew to about 15cm long and about 8mm wide. They secreted successive cone-like external skeletons in formations that look like stacked-up ice-cream cones, with each Cloudina living in the top “cone” furthest from the reef, she said.
It was thought that life on earth remained relatively basic until the Cambrian Explosion. But the discovery of complex, multicellular animals with external skeletons living on a reef made of their dead skeletons suggests that life before the Cambrian was already in an intense struggle for existence.
“The critical thing is that the Cambrian Explosion was a pretty critical event. It established that animals were responding to complicated ecological pressures and yet here we have a reef system that shows this was going on much earlier than we thought,” said Professor Wood.
“Modern reefs are major centres of biodiversity with sophisticated ecosystems. Animals like corals build reefs to defend against predators and competitors. 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 get to understand,” she said.
An analysis of the reef shows that the skeletal structures were cemented together and pointing in the same direction, which was probably towards the ocean currents carrying the floating items of food that the filter feeders lived on.
“This animal was clearly responding to some ecological pressure in the environment such as competition for space or predators. It possibly pushes the roots of the Cambrian Explosion even further back in time,” Professor Wood said.
Source: www.independent.co.uk
