Skeletons in the pre-Cambrian closetJanuary 7, 2011 By Michael Schirber Skeletons in the pre-Cambrian closet
A menagerie of strange creatures emerged during the Cambrian explosion. Credit: D. W. Miller
The Cambrian explosion marked a major blossoming in the tree of life around 540 million years ago. Nearly all of the major phyla in the animal kingdom appeared in a sudden burst of evolution. One of the drivers of this rapid diversification was likely the appearance of skeletal-bearing animals a mere 10 million years before. Researchers are studying these first skeletons to gain a better understanding of what led to their development.
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www.Groupon.com/Madison We have long taken for granted the benefit of a hard skeleton. Vertebrates like ourselves can grow large and nimble thanks to bones containing calcium and phosphorous. Mollusks and other animals are protected by shells made of calcium carbonate, whereas certain sponges construct an internal framework of silica to help them filter food.
"It is hard to imagine that life would have advanced very far without skeletons," says Shuhai Xiao from Virginia Tech.
The first instance of biomineralization – i.e. the biologic use of minerals – was around 2 billion years ago when certain bacteria precipitated grains of magnetite to apparently help orient themselves in the Earth's magnetic field. However, the first animal skeletons didn't appear until right before the Cambrian explosion, at the end of the Ediacaran Period.
These early shell-bearing creatures help to resolve Charles Darwin's concern over the sudden appearance of so many new animal species during the Cambrian explosion. The fossil record gives the impression of a "Creation" event, but in reality, animals had evolved prior to the explosion. They just didn't leave much for paleontologists to find until they developed the skeleton-making trait.
And once a few animals started building with minerals, a "housing boom" erupted across the animal kingdom. In order to understand the driving factors of this biomineralization event, Xiao and his colleagues are studying the first skeleton-builders at a unique site in China. They want to find out what kind of organisms these Pre-Cambrian organisms were, and whether they left any descendents. They will be doing this work with help from the NASA Astrobiology: Exobiology and Evolutionary Biology program.
http://www.physorg.com/news/2011-01-skeletons-pre-cambrian-closet.html