Chinese fossil eggs show dinosaur decline before extinction

Chinese fossil eggs show dinosaur decline before extinction

Artist’s illustration of a Late Cretaceous oviraptorosaur, hadrosaur and tyrannosaur that lived in central China. Credits: IVPP

About 66 million years ago, a large asteroid struck Earth and contributed to the global extinction of the dinosaurs, leaving birds as their only surviving descendants.

Scientists know that many types of dinosaurs lived around the world at the end of the Cretaceous period, just before their extinction. However, scientists have debated whether dinosaurs were at their peak or were already in decline before their demise. In other words, did the dinosaurs go out with a bang or a whisper?

His colleagues along with researchers from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences now have the answer. They have found evidence to support the hypothesis that dinosaurs were not very diverse prior to their extinction and declined overall during the last part of the Cretaceous.

their conclusions. were published in PNAS on 19 September.

mostly scientific data The last days of dinosaurs come from North America. Although some published studies suggest that dinosaur populations were growing well before the extinction, other more detailed research has suggested that dinosaurs were in decline, which set the stage for their mass extinction.

By examining dinosaur records in China, Chinese researchers hope to determine whether this declining trend extends to Asia as well.

Researchers studied more than 1,000 fossil dinosaur eggs and eggshells from the Shenyang Basin in central China. These fossils came from rock sequences with a total thickness of ~150 m. The researchers analyzed more than 5,500 geological samples and applied computer modeling to obtain detailed age estimates of the rock layers. This allowed scientists to create a Time About 2 million years at the end of the Cretaceous – with a resolution of 100,000 years – represents the period just before the extinction. This timeline allows for direct comparison with data from around the world.

The scientists identified a decline in dinosaur diversity based on Shenyang Basin data. For example, 1,000 dinosaur egg fossils collected from the basin represent only three distinct species: Macrolithus yaotunensis, Elongatolithus elongatus and Stromatolithus pinglingensis. In addition, two out of three dinosaur eggs Ospis is from a group of toothless dinosaurs known as oviraptors, while another is from the plant-eating hadrosaurid group (also known as duck-billed dinosaurs).

Some additional dinosaur bones from this area suggest that tyrannosaurs and sauropods also lived in the area between 66.4 and 68.2 million years ago. This low diversity of dinosaur species persisted in central China for the last 2 million years before the mass extinction. The small numbers of dinosaurs in the Shenyang Basin and central China are far from the world depicted in Jurassic Park.

These results – combined with data from North America – suggest that dinosaurs were probably declining globally before their extinction.

This worldwide, long-term decline in dinosaur diversity by the end of the Cretaceous period and the continued low number of dinosaur lineages over the past few million years may have resulted from known global climate fluctuations and large-scale volcanic eruptions, i.e. from the Deccan Traps. . India. These factors may have led to ecosystem-wide instability, thus making non-bird dinosaurs sensitive to mass. extinction Coincidence with the asteroid impact.


When did dinosaurs become extinct? Theories on how this happened and what survived


more information:
Low dinosaur biodiversity in central China 2 million years before the pre-Cretaceous mass extinction, Proceedings of the National Academy of Science (2022). DOI: 10.1073/pns.2211234119

Citation: Chinese fossil eggs show the decline of dinosaurs before extinction (2022, September 19) Retrieved on 20 September 2022 from https://phys.org/news/2022-09-chinese-fossil-eggs-dinosaur-decline.html to be done.

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