(LINKS TO PAST FOSSIL FRIDAYS)
Community
College (LRCCD)
Geology & Earth Science Instructor: Arthur Reed, P.G.
Happy Fossil Friday!
Friday May 14, 2021
Unlaid
egg discovered in ancient bird fossil
In
the early Cretaceous in what is now northern China, a small bird (Avimaia schweitzerae) died, sank
to the bottom of a shallow lake, was buried by sediment, and survived as a
fossil. A thorough investigation into the cause of its death was carried out
110 million years after it died by several researchers which included experts
in the filed of avian reproduction. You see, the
fossil of this bird was found with an unlaid egg still inside its body.
Characteristics of the eggshell indicated its death was likely the results of
carrying the egg too long…for some reason it was not able to lay the egg. This
fossil was found in the mid-2000’s, and the resulting research was published in
March 2019 in the journal Nature Communications.
A
brief overview of the study is given by the American Association for the
Advancement of Science is provided below, and the complete study is available
in Nature Communications (1st link below). Seven of the authors of the original
study are researchers in Beijing, China, and one is a researcher at the
Carnegie Museum of Natural History in Pennsylvania. It is refreshing to me to
see this type of international collaboration in science.
~~~~~~~~~~~~~~
Article
from scienceMag.org
In
this illustration, a colony of Avimaia schweitzerae nests on a lakeshore in what would become
northwest China. Somehow, one female ended up dead in the water—eventually
yielding the first fossil bird ever found with an unlaid egg inside.
ILLUSTRATION
BY MICHAEL ROTHMAN
Photograph
and line drawing of the holotype of Avimaia schweitzerae, IVPP V25371
Unlaid
egg discovered in ancient bird fossil
By John PickrellMar. 20, 2019 , 6:00 AM
For
the first time, researchers have found an unlaid egg inside a fossilized bird.
The find—belonging to a sparrow-size flyer that lived in northwestern China 110
million years ago—is especially remarkable because fully formed eggs typically
only stay within an adult bird for about 24 hours.
Researchers
were initially puzzled by the discovery, as they never suspected the unusual,
squashed mass within the headless fossil’s abdomen (seen as a flattened brown
layer in the center of the picture) could be an egg. But a microscopic analysis
of a fragment revealed it to be eggshell. Further study suggested structural
abnormalities that hint that the egg may have been
the cause of this bird’s demise, the paleontologists report today
in Nature Communications.
The
fossil eggshell’s structure doesn’t have the correct proportions seen in
healthy eggs and consists of multiple layers of shell. This indicates a
condition called “egg-binding,” where an egg becomes trapped inside a bird, the
team argues. This can occur in chickens and small varieties of modern pet birds
under stress and likely also led to the death of this long-lost, dinosaur-era
relative.
This
makes the discovery “the oldest documented case of this common reproductive
disorder,” the researchers say. Intriguingly, the eggshell features microscopic
spheres of calcium phosphate, which is seen today in birds that nest in humid,
infection-prone environments. This waterproofing suggests it was a species that
nested near water and buried its eggs in the ground.
The
team has christened the bird Avimaia schweitzerae. (Avimaia means
“mother bird”; and schweitzerae honors
paleontologist Mary Schweitzer.)
doi:10.1126/science.aax3954
Location
in China where fossil was uncovered.