By Chase Hill / March 21, 2019

The First Fossil Bird Found With an Unlaid Egg

The fossils are about 115 million years old.

egg fossil bird
For the first time, researchers have discovered bird fossils with an intact egg. (Getty Images)

“I couldn’t even sleep at night…I was like, my god, this is an egg!” recalls Alida Bailleul, a postdoctoral researcher from China at the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP).

Keeping her up at night was the thrill of discovering the fossils of a mother bird called the Avimaia schweitzerae and an unhatched egg.

“We were not expecting anything interesting, but it turned out to be the first fossil bird ever found with an egg inside its body,” Bailleul, the study’s lead author said.

The discovery of the egg could help researchers learn more about reproductive disorders in ancient birds as well as nesting behaviors, which are similar to that of dinosaurs and today’s dino relatives — birds.

Although this discovery was recently made, the fossils were found and stored by the IVPP in the mid-2000s. When Bailleul came to the institute for her postdoctoral work, she randomly selected the fossil because it contained soft tissue, of which she was a specialist.

Bailleul was able to confirm the existence of a calcium reservoir in the reproductive system called the medullary bone. The same bone has also been found in the Tyrannosaurus rex.

Jasmine Wiemann, a Ph.D. student at Yale is equally excited about the new find: “This is a spectacular fossil with a lot of potential for future paleobiological investigations,” she says in an email to National Geographic. “I would be thrilled to analyze pigment contents in this eggshell!”

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