Super-sized amoebas lumbering along the ocean floor at the bottom of the linkurl:Caribbean Sea;http://www.the-scientist.com/article/display/14827/ may shake up a long-standing debate on the timing of animal evolution, according to a paper published in today's issue of __Current Biology__."There is nothing paleontologists like more than a controversy," said linkurl:Mikhail Matz,;http://www.icmb.utexas.edu/cmb/directory/details.asp?id=2921 a University of Texas integrative biologist and the main author on the study. "I'm looking forward to this. It's going to be fun."The evolutionary history of complex animals - those that are composed of multiple cells and have bilateral symmetry - is marked by a dramatic burst of speciation, called the linkurl:Cambrian explosion,;http://www.the-scientist.com/article/display/12127/ about 542 million years ago. The Cambrian explosion has always been somewhat troubling to evolutionary biologists - starting with linkurl:Charles Darwin;http://www.the-scientist.com/news/display/54632/ - because of the seeming rapidity with which complex animal groups appear to have evolved.Some researchers point to rare Precambrian linkurl:"trace fossils";http://www.geo.ucalgary.ca/~macrae/t_origins/carbbones/burrow.html - such as slither prints left...

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