Dinosaurs were flourishing just before they were killed off

Dinosaurs were flourishing just before they were killed off. Most scientists agree that dinosaurs were killed off at the end of the Late Cretaceous period by a large asteroid impact, which was likely combined with intense volcanic activity. On the other hand, many experts disagree on the overall state of the dinosaurs just before they were wiped out.

A new study led by Imperial College London has found that dinosaurs had survived millions of years of long-term climate changes and were flourishing at the time of the devastating asteroid strike. This discovery contradicts the findings of previous studies which concluded that the dinosaurs were in a state of decline when they were killed.

Study lead author Alessandro Chiarenza is a PhD student in the Department of Earth Science and Engineering at Imperial.

“Dinosaurs were likely not doomed to extinction until the end of the Cretaceous, when the asteroid hit, declaring the end of their reign and leaving the planet to animals like mammals, lizards and a minor group of surviving dinosaurs: birds,” said Chiarenza.

“The results of our study suggest that dinosaurs as a whole were adaptable animals, capable of coping with the environmental changes and climatic fluctuations 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.”

North America, where many Late Cretaceous dinosaurs are preserved, was split in half by a body of water during this time period. A steady supply of sediment from the newly forming Rocky Mountains created the perfect conditions for fossilization in the west, but the conditions in the eastern half of the continent were not nearly as suitable for fossilization. For this reason, far more dinosaur fossils are found in the western half of North America and this fossil record has been used for most research.

“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,” said study co-author Dr. Philip Mannion from the University College London.

The research team used a technique known as “ecological niche modeling,” which accounts for the environmental conditions that a particular species needs to survive.  This made it possible for the experts to gain new insight into where dinosaur species would have survived, rather than simply basing their existence on where fossils had been recovered.

The study revealed that habitats which could support a range of dinosaurs were more widespread at the end of the Cretaceous than what was thought. The previously unknown territories were located in regions that were less likely to preserve fossils. This means that the number, as well as the diversity, of dinosaurs that were alive in the Late Cretaceous has been largely underestimated.

The research is published in the journal Nature Communications.

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By Chrissy Sexton, Earth.com Staff Writer

Image Credit: Davide Bonadonna