This 250-million-year-old fossil proves mammal ancestors laid eggs

By Jack Guy, CNN (CNN) — Researchers studying a 250-million-year-old fossil have found the first ever proof that mammal ancestors laid eggs, with the discovery also shedding light on a remarkable survival story. The fossil, found in South Africa, belongs to a tightly curled embryo of a Lystrosaurus, a mammal ancestor famous for surviving an