Unveiling the Secrets of China’s Yixian Formation: The Remarkable Preservation of 125-Million-Year-Old Dinosaur Fossils

Table of Contents

• 1 Ancient Fossils in the Yixian Formation
• 2 Why are fossils perfectly preserved?
  • 2.1 Fossils from 125 million years ago
• 3 ‌What unique insights into prehistoric life have ⁤been gained from the ⁣well-preserved ‍dinosaur fossils found in the Yixian Formation?

Dinosaurs and other ancient animals lived hundreds to hundreds of millions of years ago. However, in one place in China, these fossils are still well preserved. How come?

Usually, ancient fossils found today tend to be left over, incomplete. Compared to most, in the 1990s in the Yixian Formation, China, many remains of dinosaurs, birds, mammals, insects, frogs, turtles and other creatures were found.

Before that, between about 120 million and 130 million years ago, during the time of the dinosaurs, the northeastern region of China was still temperate forests and lakes and was home to an ecosystem of ancient creatures.

Strangely, various fossils from that time were undisturbed until the 1980s, when villagers began to discover well-preserved creatures.

Ancient Fossils in the Yixian Formation

The fossils found are different from fossils in general. Discoveries include cat-sized mammals and small dinosaurs locked in deadly combat, pausing mid-action when they died. These fossils were found to be complete, including internal organs, feathers, scales and stomach contents.

This discovery shows that the fossils are well preserved. In fact, due to their excellent level of preservation, some fossils of non-avian feathered dinosaurs can be recognized for their feather color even though they have been preserved for millions of years.

This discovery changed the world of paleontology, as well as explaining how feathered dinosaurs evolved, and clearly proving that today’s birds are direct descendants of dinosaurs.

Why are fossils perfectly preserved?

The first hypothesis of scientists was that the fossils in “Yixian Formation” were suddenly buried due to volcanic activity. It is similar to the heat wave from the eruption of Mount Vesuvius that buried many citizens of Pompeii in 79 AD.

But apparently, this hypothesis is wrong. These fossils did not disappear as a result of volcanic activity, but normal events, such as the collapse of holes or water that continued to fall to sediment that eventually buried the creatures in the ground and died by run out of oxygen.

This discovery was revealed thanks to a study published in the journal Proceedings of the National Academy of Sciences on November 4, 2024 by Paul E Olsen and his friends. In the new study, researchers used advanced technology and revealed that the fossils found were less than 93,000 years old and were not associated with any particular event.

“This is probably the most important dinosaur discovery in the last 120 years,” said Paul Olsen, study co-author and paleontologist at the Lamont-Doherty Earth Observatory, Columbia School of Climate, quoted from phys.org.

They found that the fossils from Yixian came in two types, namely complete 3D skeletons, perfectly articulated from sediments that formed mostly on land, and smooth but highly detailed carcasses that they were found in lake sediments, some with soft tissue.

Fossils from 125 million years ago

To determine the age of the fossils, the study’s lead author, Scott MacLennan of the University of the Witwatersrand in South Africa, analyzed small particles of the mineral zircon, taken from nearby rocks and the fossils themselves.

Using modern technology, researchers have confirmed that these fossils are approximately 125.8 million years old. Not only that, several previous studies also show that there are three periods that are affected by the Earth’s orbit and very wet weather.

It is this situation that creates sediment in lakes and land​​​​​​ and burying these creatures and keeping them from being exposed to oxygen that accelerates decomposition. The effect is to make soft tissue from fossils that have still been found, such as feathers and preserved skin.

Upon further investigation, it was found that the particles around the bones were better indicating that the process of decomposition started after the burial.

“There was enough oxygen around for bacteria or insects to damage at least the animal’s skin and organs,” the researchers said.

Olsen also said that the collapse of a hole could be the cause of death for some creatures. For example, mammals that try to attack dinosaur holes to try to eat or injure.

Although the Yixian deposit is famous for its fossils, Olsen believes that fossils may be found in similar settings elsewhere in the environment with similar conditions.

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