They are often depicted as going out with a “bang” after a giant asteroid struck Earth 66 million years ago.
But a new study suggests the dinosaurs were more likely to go out with a “whine.”
Researchers from the Chinese Academy of Sciences examined more than 1,000 fossilized dinosaur eggs and eggshells and claim the animals were already in decline when the asteroid struck – possibly as a result of climate change.
“Our results support a long-term decline in global dinosaur biodiversity 66 million years ago that likely set the stage for the mass extinction of nonavian dinosaurs at the end of the Cretaceous,” the team wrote in their study published in PNAS.
They are often depicted as going out with a “bang” after a giant asteroid struck Earth 66 million years ago. But a new study suggests the dinosaurs went out with a “whine” rather than a bang
Researchers from the Chinese Academy of Sciences examined more than 1,000 fossilized dinosaur eggs and eggshells and claim the animals were already in the process of decay when the asteroid struck
Dinosaurs ruled and dominated the earth until about 66 million years ago.
A six-mile-wide asteroid called Chicxulub crashed into what is now Mexico, triggering a mass extinction that killed more than 75 percent of Earth’s species.
While previous studies have shown that a multitude of dinosaurs were on Earth just before the asteroid struck, it was previously unclear whether they were in their prime or already in decline.
Most of the data on dinosaurs’ last days comes from North America, but for this study the researchers used records in China.
The team examined over 1,000 fossilized dinosaur eggs and eggshells from the Shanyang Basin in central China. These fossils come from rock sequences that the researchers were able to age using computer models
Their results suggest that dinosaur diversity has declined over the span of two million years, with the 1,000 egg fossils belonging to just three species – Macroolithus yaotunensis, Elongatoolithus elongatus and Stromatoolithus pinglingensis
The team examined over 1,000 fossilized dinosaur eggs and eggshells from the Shanyang Basin in central China.
These fossils come from rock sequences that the researchers were able to age using computer models.
This allowed them to create a timeline from nearly two million years to the end of the Cretaceous period – the period just before extinctions – which could then be compared to data from around the world.
Their results suggest that dinosaur diversity has declined over the span of two million years, with the 1,000 egg fossils belonging to just three species – Macroolithus yaotunensis, Elongatoolithus elongatus and Stromatoolithus pinglingensis.
While the reason for this decline that led to the asteroid remains unclear, researchers have several theories
The team examined over 1,000 fossilized dinosaur eggs and eggshells from the Shanyang Basin in central China
A few other dinosaur bones have been found in the region, showing that tyrannosaurs and sauropods also inhabited the area around 66.4 and 68.2 million years ago.
“The small number of dinosaurs in the Shanyang Basin and central China is a far cry from the world depicted in Jurassic Park,” the team said in a statement.
While the reason for this decline that led to the asteroid remains unclear, researchers have several theories.
“This global, long-term decline in dinosaur diversity up to the end of the Cretaceous and the persistently low numbers of dinosaur lineages over the past few million years may be due to known global climate variability and massive volcanic eruptions, i.e. the Deccan Traps in India,” they suggest .
“These factors may have led to ecosystem-wide instability, leaving non-avian dinosaurs vulnerable to a mass extinction event that coincided with the asteroid impact.”
HOW DINOSAURS WENT EXTINCT AROUND 66 MILLION YEARS AGO
Dinosaurs ruled and dominated the Earth about 66 million years ago before suddenly becoming extinct.
This mass extinction is known as the Cretaceous-Tertiary extinction.
For many years it was believed that climate change was destroying the giant reptiles’ food chain.
In the 1980s, paleontologists discovered a layer of iridium.
This is an element that is rare on Earth but found in large quantities in space.
When this was dated, it coincided exactly with the time when dinosaurs disappeared from the fossil record.
A decade later, scientists discovered the massive Chicxulub Crater at the tip of Mexico’s Yucatán Peninsula, dating from the period in question.
The scientific consensus now says that these two factors are linked and both were likely caused by a giant asteroid crashing into Earth.
With the projected size and impact speed, the collision would have created an enormous shock wave and likely triggered seismic activity.
The fallout would have created plumes of ash that likely covered the entire planet, making it impossible for the dinosaurs to survive.
Other animal and plant species had a shorter span of time between generations, which allowed them to survive.
There are several other theories as to what caused the demise of the famous animals.
One early theory was that small mammals ate dinosaur eggs, and another proposes that toxic angiosperms (flowering plants) killed them.