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This fossil of an ancient bird that died with an unlaid egg still inside her body is believed to be the first of its kind.
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Scientists have discovered the first fossil bird ever found with an egg preserved inside its body, a new study reports.

The 110-million-year-old bird is a new species called Avimaia schweitzerae, which was discovered in northwestern China. The bird lived at the same time as the dinosaurs. 

The discovery was a surprise to paleontologists: “We were not expecting anything interesting, but it turned out to be the first fossil bird ever found with an egg inside its body,” study lead author Alida Bailleul of China’s Institute of Vertebrate Paleontology and Paleoanthropology told National Geographic.

The finding is especially amazing because fully formed eggs typically only stay within an adult mama bird for about a day, according to Science magazine.

But problems with the egg itself may have caused the bird’s death due to “egg-binding.” This happens when the egg becomes stuck inside the body, preventing the egg from being laid, and killing the mother bird, the study said. Egg-binding is a serious and lethal condition that is fairly common in small birds undergoing stress.

This condition still occurs in chickens and modern pet birds.

Yet despite being malformed, the egg is excellently preserved, including parts of the eggshell that are seldom seen in the fossil record, such as traces of the egg membrane and the cuticle,

Overall, the scientists said this fossil provides more information about ancient reproduction than any other Mesozoic fossil bird yet discovered. 

As for the species name, it means “mother bird” (Avimaia) and also honors paleontologist Mary Schweitzer (Schweitzerae). 

The study was published in the peer-reviewed British journal Nature Communications.

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