Paleontologists identify 250-million-year-old fossil egg of mammal ancestor

Paleontologists found a 250-million-year-old fossil egg with a mammal-ancestor embryo inside.

The embryo was identified as Lystrosaurus.

The find is the first direct fossil evidence that early mammal ancestors laid eggs.

Julien Benoit led the study; the fossil was first found in South Africa in 2008 and scanned at ESRF.

The embryo's unfused lower jaw shows it could not eat on its own, and Lystrosaurus laid soft-shelled eggs.