The Cambrian Period is a time when most phyla of marine invertebrates first appeared. Also dubbed the 'Cambrian explosion,' fossilized records from this time provide glimpses into evolutionary biology. Most fossils show the organisms' skeletal structure, which may give researchers accurate pictures of these prehistoric organisms. Now, researchers have found rare, fossilized embryos they believe were undiscovered previously. Their methods of study may help with future interpretation of evolutionary history.

Source: Rare fossilized embryos more than 500 million years old found