A recently analyzed fossil of a Lystrosaurus hatchling has helped solve a decades-old mystery A recently analyzed 250 million-year-old fossil has shown that early mammals laid eggs, according to a paper published in the PLOS One journal on Thursday. While some examples of egg-laying mammals exist today, such as the platypus and the echidnas, scientists have spent decades looking for proof of this in earlier ancestors. According to South African Professor Jennifer Botha, one of the scientists