A famous fossil bed in northeastern China’s Yixian region has revealed some of the most impressive and best-preserved dinosaur fossils on record. Archaeologists excavating the area over the past 60 years have discovered numerous intact skeletons, as if time had stopped at the exact moment they died. Feathers and other intact soft tissue samples found in some fossils helped prove that modern birds are almost certainly descendants of dinosaurs.
Until now, scientists have mainly attributed the unique preservation of these fossils to a series of sudden and violent volcanic eruptions, similar to the one that turned the doomed inhabitants of Pompeii into so-called “volcanic eruptions.” That’s what I thought.mummy ash” Some researchers citing this theory refer to this formation colloquially as “Pompeii in China.But new archaeological evidence casts doubt on this dramatic supposed dinosaur catastrophe. in fact, According to new research Published in Proceedings of the National Academy of Sciences According to (PNAS), these animals may have died from more mundane events, such as burrow collapses or particularly seasonal heavy rains.
“these [fossils] “These are just snapshots of daily mortality under normal conditions over a relatively short period of time,” Paul Olsen, a paleontologist at the Columbia Climate School and study co-author, said in a statement.
Some animals appear to have died in their sleep
Fossils discovered in the Yixian formation can be broadly classified into two different categories. The first is an almost completely intact 3D geological formation, primarily from deposits found on land. One of the camp’s most famous fossils depicts a cat-sized mammal in a deadly fight with a small dinosaur. The second category of fossils are flat, highly detailed carcasses typically found in lake sediments. Although this second group has less dimensionality than the others, it is highly valuable because some of it contains soft tissues such as internal organs, feathers, and scales that are not normally preserved in the fossil record. It is believed that there is.
Previous theories held that these creatures were essentially frozen over time after being exposed to extremely hot “pyroclastic flows” of volatile ash spewing from nearby volcanoes. However, researchers noticed some important differences between the Chinese samples and the human bones found at Pompeii. In the latter case, the red-hot ash burned off the hair and skin of the deceased. Humans were also found hunched over in a “punitive posture” in Pompeii, suggesting an extremely painful and violent outcome. In contrast, many of Yixian’s fossilized animals have their tails and arms tucked comfortably around their bodies, nestled together. Research records show that some of these dinosaurs and mammals appeared to be fast asleep the moment they died.
To better understand what happened, the researchers analyzed tiny particles of zircon taken from some of the fossil samples in the formation and surrounding rock. They then used an advanced technique called chemical abrasion isotope dilution thermal ionization mass spectrometry (CA-ID-TIMS) to determine the age of the samples. The fossil samples date back 125.8 million years and appear to have occurred within 93,000 years of each other. Rather than one sudden extinction event, the researchers linked the fossil to three periods when changes in the Earth’s orbit created wetter environments.
Researchers say this increased moisture may have caused sediment to build up in lakes and land faster than previously thought. That loose sediment may have quickly buried the animals, cutting off the oxygen bacteria and insects need to survive and help decompose. The absence of oxygen and bacteria may have helped preserve the soft tissue of the flattened lake fossils. In contrast, more three-dimensional, upright fossils found on land were less sealed, which may explain why only the bones were preserved. At the same time, core samples of the rock surrounding the fossil tended to be coarse-grained, whereas samples immediately surrounding the fossil were much finer-grained. These details, along with the moisture in the sediment, suggest that the animals likely died suddenly from the collapse of their burrow, rather than a large-scale volcanic eruption.
“The preservation of flat and three-dimensional fauna is not the result of a series of catastrophic volcanic events such as Pompeii,” the researchers said. “Rather, these deposits are millennial-scale geological snapshots of the era of diverse continental assemblages repeatedly sampled by cyclical environmental processes and normal attrition of assemblages.”
Although the exact cause of the burrow collapses that occurred around the area are still not fully understood, the new study suggests that they are likely less dramatic than previously proposed volcanic cataclysms. Suggests. Burrow collapses are still relatively common today and can potentially result from overhearing solid objects or larger animals, in this case dinosaurs, walking around. This latter theory may also help explain why well-preserved fossils in the Yixian formation tend to contain only small dinosaurs.
“The stories told about how they were preserved highlight important human biases,” Olsen added. “It is attributing extraordinary causes, or miracles, to everyday events when we do not understand their origins.”
