Unveiling the Hidden History of China

A Series of Unfortunate Events, Not Volcanic Eruptions, May Have Buried the Cretaceous Creatures

The Famous Fossilized Nest of Juvenile Psittacosaurus Dinosaurs and One Older Individual

A new study proposes that this famous fossilized nest of juvenile Psittacosaurus dinosaurs and one older individual may have formed when a burrow they were sheltering in collapsed. This is contrary to the previous belief that the diverse members of this ancient community were abruptly buried by catastrophic volcanic flows of hot ash and rock.

The Yixian Formation

The Cretaceous Period rock layers, known as the Yixian Formation, are famous for two types of fossils: A collection of still-perfectly articulated skeletons preserved in 3-D relief; and fossils that are flattened but bear exquisitely preserved details, such as feathers, pigments, soft tissues, and even stomach contents. It was these feathery details that ultimately helped convince paleontologists that modern birds evolved from theropod dinosaurs.

The New Study

One of the most extraordinary fossil beds of Cretaceous creatures in the world formed about 125 million years ago, in what’s now northeastern China. Researchers have thought that the diverse members of this ancient community were abruptly buried by catastrophic volcanic flows of hot ash and rock. However, a new study proposes that this famous fossilized nest of juvenile Psittacosaurus dinosaurs and one older individual may have formed when a burrow they were sheltering in collapsed.

The Famous Fossil Bed

The Study’s Findings

The team used a very precise geochemical dating technique to analyze tiny zircon minerals collected from the rocks containing the fossils, as well as from two dinosaur fossils that were originally from the site but are now in a museum. These dates revealed that both of the Yixian’s fossil beds date to within just 93,000 years of each other, a geological blip in time.

The researchers used a very precise geochemical dating technique to analyze tiny zircon minerals collected from the rocks containing the fossils, as well as from two dinosaur fossils that were originally from the site but are now in a museum. These dates revealed that both of the Yixian’s fossil beds date to within just 93,000 years of each other, a geological blip in time.

The Sedimentation Rate

The core finding of the paper concludes that the sedimentation rate when the fossils formed was extremely high. However, this doesn’t necessarily mean that volcanism wasn’t the main culprit. The team’s study analyzed only two individual specimens, not enough to draw that conclusion.

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A New Hypothesis

The researchers say that it wasn’t a single catastrophic event that did in all of the creatures. Cores drilled into the Yixian Formation at several different locations revealed the 3-D fossils to be older, lying beneath the rock layer containing the flattened fossils. A layer of hardened lava lies in between the two.

The New Theory

The team devised a new hypothesis for how all these creatures died. Instead of a dramatic sudden mass death, the researchers say, the Yixian Formation represents “a brief snapshot of normal life and death in an Early Cretaceous continental community.” The 3-D fossils include skeletons of Psittacosaurus and other dinosaurs, apparently in nests.

The Debate

The team’s study analyzed only two individual specimens, not enough to draw a conclusion. However, MacLennan and colleagues argue that it’s a logical fallacy that a remarkable bonebed must have a remarkable origin. The volcanic debris at the site may have thrown researchers off the scent of the true culprit behind the deaths.

The New Findings

The core finding of the paper concludes that the sedimentation rate was extremely high, but that doesn’t necessarily mean that volcanism wasn’t the main culprit. However, the team’s study analyzed only two individual specimens, not enough to draw a conclusion.