Avimaia, a fossil bird found with an unlaid egg

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A new genus of bird from the Late Cretaceous Xiagou Formation of northwest China has been described. The specimen was fossilized with an egg still inside of it, making it the first pregnant fossil bird ever found. The new genus has been given the name Avimaia schweitzerae ("Schweitzer's bird mother"), with the genus name originating from the specimen being found with an unlaid egg inside of it and the species name originating from Mary Schweitzer, a paleontologist who described the first instance of medullary bone in Tyrannosaurus rex. Avimaia is believed to possess medullary bone, making it potentially the first fossil found with both medullary bone and an egg. If medullary bone is present in the specimen, it will help to show the connection between medullary bone and avian reproduction. It is believed that the egg was left unlaid due to a pregnancy complication, likely "egg binding", which may have been the cause of the bird's death. This specimen could help to reveal new information on reproductive disorders in ancient birds. In addition, if pigment is preserved in the egg, the fossil could reveal more about how ancient birds nested. The egg has already been determined to have had a glossy sheen similar to the egg of the modern tinamou. The fossil was first discovered in the mid-2000s, but the egg wasn't noticed for what it was and was kept in storage. Later, in 2018, researchers realized that there was a fossilized egg in the specimen, leading to its eventual description in 2019. Here is an image of the specimen and a reconstruction of the animal by artist Micheal Rothman, as well as a link to the paper describing the new genus.




Paper (open access!) https://www.nature.com/articles/s41467-019-09259-x

[Halichoeres]

Took me a second to spot the submerged bird in the reconstruction; until that moment it looked so idyllic! Thanks for posting this.