About 110 million years earlier, a sparrow-sized bird passed away with her egg still inside her body. That egg, crushed and flattened by pressure in time, is the initially unlaid bird egg understood to be maintained in a fossil, scientists report March 20 in Nature Communications

The fossil was discovered 11 years earlier in northwestern China. In 2018, paleontologists led by Alida Bailleul of the Secret Lab of Vertebrate Advancement and Human Origins in Beijing took a more detailed look, and saw something odd: The bird had a weird sheet of tissue in between her pubic bones. Taking a look at a piece of the tissue under a microscopic lense, Bailleul discovered that it was from an egg.

The bird, a freshly recognized types, was called Avimaia schweitzerae in honor of paleontologist Mary Schweitzer’s deal with fossilized soft tissues( SN: 12/24/16, p. 15). More analyses exposed more surprises. The mom bird’s skeleton includes traces of medullary bone, a calcium-bearing tissue that help in eggshell development( SN: 4/16/16, p. 16). It’s the greatest proof yet that ancient birds produced this tissue throughout recreation.

And the egg’s cuticle, the outer layer of shell, includes small mineral spheres comparable to spheres in the egg cuticles of modern-day waterfowl such as quails and ducks. The spheres, believed to safeguard embryos from microbial infections, have actually never ever in the past been seen in any fossilized eggs.

However all was not well with this bird and her embryo. The eggshell has 2 layers rather of the typical one, recommending that the egg had actually stayed too long in the abdominal area. And the egg’s layers are very thin, thinner than a sheet of paper. In modern-day birds, especially little birds experiencing severe tension, these signs can suggest a lethal condition referred to as egg-binding, in which a bird is not able to lay the egg. In truth, the scientists recommend, the unlaid egg might have eventually eliminated the mom.