MINUTE fossils have helped pin down a key step in the early evolution of animals by showing that internal complexity came before large size.
The first animals were simple blobs like sponges, but at some point they evolved bilateral symmetry – a two-sided body plan. Genetic evidence suggested this split occurred about 600 million years ago, but no fossils had been found to prove it.
Jun-Yuan Chen of the Nanjing Institute of Geology and Palaeontology in China and his team have found 10 fossils in rocks 580 to 600 million years old from China. The 0.2-millimetre-long oval animals have a mouth,…
