[Rockhounds] Fossil egg analysis in China adds to debate of what may have caused dinosaurs’ demise

[Kreigh Tomaszewski]

It’s a hard-fought paleontological debate. Did the massive asteroid that
struck Earth 66 million years ago
<https://www.cnn.com/2022/02/23/world/asteroid-dinosaur-extinction-spring-scn/index.html>
wipe
out a thriving and diverse population of dinosaurs, or were they already
struggling to survive when that cataclysmic day dawned?

Most information on dinosaurs at the end of the Cretaceous era comes from
what is now the United States, particularly the Hell Creek Formation
<https://edition.cnn.com/2022/05/11/world/dinosaur-apocalypse-tanis-fossil-site-scn/index.html>
, which provides a picture of relatively rich dinosaur diversity during the
final million years of that period.

However, fossil information from that time in other regions is much
thinner, and it’s not known whether the pattern seen in North America is
representative of global dinosaur diversity then.

To fill in this gap in the fossil record, researchers in China have studied
more than 1,000 fossilized dinosaur eggs from the Shanyang basin in central
China. Dinosaur diversity was already on the wane at the end of the
Cretaceous, suggested the study, published September 19 in the scientific
journal Proceedings of the National Academy of Sciences
<https://www.pnas.org/doi/abs/10.1073/pnas.2211234119>.

The eggs and eggshell fragments represent the last 2 million years of the
dinosaur era, with fossils representing each 100,000-year interval. The
study involved obtaining detailed age estimates of rock layers by analyzing
and applying computer modeling to over 5,500 geological samples.

The analysis found whole eggs and eggshell fragments from just three
species of dinosaurs, which suggested low dinosaur biodiversity during that
time period, the researchers said.

https://www.cnn.com/2022/09/23/world/dinosaur-egg-fossils-extinction-scn/index.html