CHINA - A majestic fossil of a bird that is about to lay an egg was found in the mid-2000s in modern-day northwest China. The fossil was noted to have an unidentified membrane remnant and was put in storage.
Recently, the researchers have discovered the unlaid egg that was still inside the fossilized bird. The sparrow-sized flyer lived about 115 million years ago. Researchers stated that fully formed eggs usually have only 24 hours to spend inside an adult bird.
The initially puzzling discovery was described to be a fossil of a headless bird with a squashed mass in its abdomen. Later, tests revealed that the flattened brown layer is fragments of an eggshell. Other studies suggest that there were structural abnormalities and was seen to be the reason for the bird's death.
The eggshell found in the fossil did not have the correct structure that a healthy egg should have. It also has multiple layers of eggshell that occurs during "egg-binding." This happens when the egg gets stuck near the cloaca. The shell would continue to grow and would get stuck inside the bird's body. However, the researchers found no trace of the embryo in the shell which prompts for more studies and researches.
The team also found what they believe is the medullary bone, a temporary bone structure that facilitates eggshell production by storing calcium. Although other previous finds have also yielded results of avian fossils having such bone structure, this is the first time that scientists were able to find it together with the presence of an egg inside the adult bird. This then established a strong link between the medullary bone and the evolution of avian reproduction.
The prehistoric species was called Avimaia schweitzerae after Mary Schweitzer, a paleontologist at North Carolina State University.
Schweitzer was part of the team that found a potential medullary bone in a Tyrannosaurus Rex in 2005. The paleontologist stated that the link is strong but tests should still be done before concluding anything.
University of Hong Kong paleontologist Michael Pittman values this discovery as the best insight into the reproduction of the Enantiornithines which is a diverse group of early bird in the Cretaceous period. The species were said to hatch out of its egg running and possibly ready to fly as well.
Other studies on the egg's color and texture may give researchers more information about the bird's habitat and its species.
