A research team focused on the fossil records of North America, examining them from 18 million years before the end of the Cretaceous period mass extinction. The new analysis suggests increasing evidence that dinosaurs were doing well before an asteroid hit Earth.

There has been a long-standing debate in paleontology: were dinosaurs still alive when an asteroid hit Earth 66 million years ago on a spring day, or were they on the brink of extinction?

To find answers, a research team examined North America’s fossil records from 18 million years before the mass extinction at the end of the Cretaceous period. A recent analysis published in the journal Current Biology contributes to the growing evidence that dinosaurs were in good shape before the deadly asteroid impact.

However, initially seen fossils available for study from that period show that the number of over 8,000 dinosaur species peaked approximately 75 million years ago and decreased in the 9 million years before the asteroid impact.

FOUR DINOSAUR FAMILIES STUDIED

In the new study, researchers analyzed four main dinosaur families: Ankylosauridae (armored herbivorous dinosaurs like the club-tailed Ankylosaurus), Ceratopsidae (large three-horned herbivores including Triceratops), Hadrosauridae (duck-billed dinosaurs), and Tyrannosauridae (carnivores like Tyrannosaurus rex).

The data was inputted into a computer model, and Dean and colleagues compared the physical fossil records with the records suggested by the model, finding a discrepancy.

HABITATS REMAINED STABLE

The model suggests that during the 18 million year period in question, the general land masses occupied by the four dinosaur clades likely remained stable, indicating that their potential habitats were stable, and the risk of extinction stayed low.

One factor that could have obscured the true diversity patterns of dinosaurs was the lack of exposed rocks on the Earth’s surface during that time frame, which is not something fossil hunters can investigate today.

“DID NOT DESTINED TO EXTINCTION”

In a statement, study co-author and Royal Society Newton International Fellow at the Department of Earth Sciences, University College London, Alfio Alessandro Chiarenza mentioned, “In this study, we suggest the high possibility that this marked drop is a result of diminishing sampling windows driven by geological changes in the fossil-bearing layers of this last Mesozoic that are dictated by processes such as tectonic movements, mountain building, and sea-level regression rather than genuine biological fluctuations in biodiversity.”

Chiarenza added, “Dinosaurs were not inevitably destined to extinction at the end of the Mesozoic. If not for that asteroid, they might still be sharing this planet with mammals, reptiles, and their surviving descendants, the birds.”