Dinosaurs were flourishing in number before the deadly asteroid strike that wiped them out 66 million years ago, a new study suggests.
For decades scientists thought the creatures were in decline before the deadly impact, as they faced huge pressures from climate change.
Now a study has shown dinosaurs species were extremely adaptable and capable of coping with the environmental changes during the last years of the Jurassic period.
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Dinosaurs were flourishing in number even in the face of climate change after the deadly asteroid strike wiped them out 66 million years ago. Here, a reconstruction of a late palaeoenvironment in North America, where a floodplain is roamed by dinosaurs
Scientists largely agree that an asteroid impact wiped out the creatures but debate whether they were already dying out before their eventual extinction.
Researchers previously used fossil records and mathematical models to suggest dinosaurs were in decline with the diversity and numbers gradually falling.
Instead the team, from Imperial College London, University College London and University of Bristol examined the environmental conditions the dinosaurs had to endure.
They looked at the changing climate coupled with the distribution of dinosaur species in North America, where many dinosaur fossils were found.
They found that habitats that could support them were much more widespread than originally thought, but these areas were less likely to preserve fossils.
During the time when the creatures walked the Earth, the continent was split in two by a large inland sea.
Far more fossils were found in the western half, from the newly forming Rocky Mountains, which created perfect conditions for fossilising dinosaurs.
In contrast, the eastern half of the continent was far less suitable for fossilisation.
This means that far more dinosaur fossils are found in the western half, and it is this fossil record that is often used to suggest dinosaurs were in decline.
Dr Philip Mannion, from University College London, said: ‘Most of what we know about Late Cretaceous North American dinosaurs comes from an area smaller than one-third of the present-day continent.
‘And yet we know that dinosaurs roamed all across North America, from Alaska to New Jersey and down to Mexico.’
The new analysis models the changing climate coupled with the distribution of dinosaur species in North America. They used climate and ecological modelling to map the abiotic niches of non-avian dinosaurs through the latest Cretaceous of North America
A global mapshowing the distribution of surface temperature over the Earth in the Late Cretaceous, ~76 million years ago. Warmer colours represent higher temperatures, while colder colours indicate lower ones
Instead of using this record, the team employed ‘ecological niche modelling’, which examines environmental conditions, such as temperature and rainfall, each species needs to survive.
The team then mapped where these conditions would occur both across the continent and over time.
This allowed them to create a picture of where groups of dinosaur species could survive as conditions changed, rather than just where their fossils had been found.
The result was they found habitats that could support a range of dinosaur groups were actually more widespread at the end of the Cretaceous, but that these were in areas less likely to preserve fossils.
The team found that habitats that could support them were much more widespread than originally thought but these areas were less likely to preserve fossils Here, the badlands of Dinosaur Provincial Park in Alberta, Canada. These rich fossil deposits were once lush floodplains dominated by dinosaurs
These potentially dinosaur-rich areas were smaller wherever they occurred, again reducing the likelihood of finding a fossil from each of these areas.
Lead researcher Alessandro Chiarenza, a PhD student of Imperial College London, said that the results suggest that dinosaurs as a whole were adaptable animals, capable of coping with the environmental and climatic changes that happened during the last few million years of the Late Cretaceous.
‘Climate change over prolonged time scales did not cause a long-term decline of dinosaurs through the last stages of this period,’ he said.
The findings were published in the journal Nature Communications.
WHY DID THE DINOSAURS GO EXTINCT?
Dinosaurs ruled and dominated Earth around 66 million years ago, before they suddenly went extinct.
The Cretaceous-Tertiary extinction event is the name given to this mass extinction.
It was believed for many years that the changing climate destroyed the food chain of the huge reptiles.
In the 1980s, paleontologists discovered a layer of iridium.
This is an element that is rare on Earth but is found in vast quantities in space.
When this was dated, it coincided precisely with when the dinosaurs disappeared from the fossil record.
A decade later, scientists uncovered the massive Chicxulub Crater at the tip of Mexico’s Yucatán Peninsula, which dates to the period in question.
Scientific consensus now says that these two factors are linked and they were both probably caused by an enormous asteroid crashing to Earth.
With the projected size and impact velocity, the collision would have caused an enormous shock-wave and likely triggered seismic activity.
The fallout would have created plumes of ash that likely covered all of the planet and made it impossible for dinosaurs to survive.
Other animals and plant species had a shorter time-span 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 off.