June 27, 2014
Discovery Of A Prehistoric Reef Built By First Hard-Shelled Animals
Gerard LeBlond for www.redorbit.com - Your Universe Online
Located on dry land in Namibia is a 550-million-year-old reef that researchers say was built by the first hard-shelled animals. It is one of the oldest reefs known and tiny aquatic fossils have revealed that the creatures developed hard protective coats and constructed the reefs for shelter and safety.
The study, led by Professor Rachel Wood of the University of Edinburgh, and collaborated on with other scientists from Edinburgh, University College London and the Geological Survey of Namibia, was published in the journal Science. The work was supported by the Natural Environment Research Council, the University of Edinburgh and the Laidlaw Trust.
The findings support previous research that revealed the same conclusions as the new study.
“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 yet to understand,” Wood, who is a Professor of Carbonate GeoScience at Edinburgh, said in a statement to The Independent.
Normally, non-living reefs are formed by a natural process of sediment deposits and erosion. However, these tiny creatures – known as Cloudina – built a living reef quite similar to the natural reefs found today. They attached themselves to a rigid surface as well as to each other by producing a calcium carbonate which acts as a natural cement.
The creatures built these reefs in an ancient sea that is now Namibia and considered to be the oldest reef of its type in the world. The tiny filter-feeding animals lived on the seabed 541 million years ago. According to fossil evidence, the creatures were soft bodied until environmental changes forced the creature to develop new behaviors and new physical features to survive.
“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,” Wood said.
The hard bodies were formed through a process called biomineralisation and most likely done for protection against predators. The competition for food was great and the reefs provided nutrient-rich currents as well as a home for the Cloudina.
Determining the age of the reef was possible by volcanic ash remains, according to the team.
“It is 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 concluded.