Wednesday , May 25 2022

Were Dinosaurs Dying Out Before the Asteroid struck? New Study Adds to Debate



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Life on planet Earth is a fragile thing. All it takes is one outward asteroid, and bam, there is the dominant group of land animals on our planet.

If it wasn’t for the 10km wide meteorite that hurt the Earth some 66 million years ago, dinosaurs could have continued to dominate the land, a newspaper suggests. For mammals like us, we may never have had a chance to get up.

The results are the latest in a long and drawn-out debate on the extinction of non-bird dinosaurs.

Although the Chicxulub asteroid and the consequences of its impact – which blocked the Sun’s rays and prompted global climate cooling – are considered major candidates for the massive Cretaceous extinction event in general, some recent evidence suggests that some species dinosaurs were already declining tens of millions of years before then.

The authors of these findings have claimed that there is “overwhelming support for long-term decline across all dinosaurs and within all three major dinosaur groups”, but among palaeontologists, support for that idea is scarce. In fact, it is highly controversial.

In the years since this idea was first introduced, several other lines of research have disagreed with its conclusions – not necessarily with the data itself, but with the interpretations drawn.

Gaps in dinosaur fossils and sampling trends mean that we may be under the sampling of certain Cretaceous dinosaurs, while overestimating the presence of others.

“Previous studies by others have used various methods to conclude that dinosaurs would have died out anyway, as they were declining towards the end of the Cretaceous,” explains paleontologist Joe Bonsor of the University of Bath.

“However, we show that if you expand the data set to include more recent dinosaur family trees and a broader set of dinosaur types, the results do not all point to this conclusion – in fact only about half of them do. “

Instead of simply counting the number of dinosaur species present at the time using fossil records, the team used statistical methods to look at the rate of speculation in dinosaur families.

Analyzing thousands of family tree combinations in 12 dinosaur families, researchers tested whether species diversification was slowing down, staying the same or accelerating before the asteroid impact – a sign that could tell us how quickly extinct dinosaurs are being replaced by new ones.

Of all 2,727 guessing models, only 518 (less than 20 percent) unambiguously showed a final decline before the asteroid impact.

Even when the authors considered those on the border of terminal decline and no deterioration, that’s just over half of the models that would support more extinction extinction.

As such, the team states that they were skeptical of the final extinction theory, suggesting instead that dinosaur diversity would have remained high throughout the Late Cruel Period, even as species richness varied between branches.

“The main point of our paper is that it is not as simple as looking at a few trees and making a decision. The large and unavoidable biases in the fossil record and lack of data can often indicate species decline, but this may not be a reflection from the reality at the time, “Bonsor said.

“At the moment our data does not show that they are declining, in fact some groups such as hadrors and keratops were thriving and there is no evidence to suggest that they would have died out 66 million years ago if the event had not happened extinction has occurred. “

The results are supported by another recent study, which found that North American dinosaur habitats had not declined during the Late Cretaceous.

Fossil outcrops for this region are small, which means we probably under-sample the area and underestimate its species richness.

Such systemic sampling errors are rife in palaeontology and, to a degree, inevitable. But depending on species richness rather than total species also comes with its limitations.

For starters, there may well be no correlation between guessing rates in dinosaur evolution and extinction. That’s an assumption we make in retrospect.

“We may never know the true levels of speculation and extinction of Mesozoic dinosaurs,” the newspaper’s authors admit, “but more focus on filling gaps in the fossil record will be the main way palaeontologists continue to build and picture more accurate of the dinosaur variety of the past. ”

The newspaper once again highlights the many gaps and prejudices in our knowledge, and the authors call for ongoing research that is rigorous, regionally managed and widely disseminated. well in time to recreate the most holistic history possible.

The study was published in the Royal Society Open Science.

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