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The amount of dinosaurs decline even before the start of mass death

12 May

The large herbivorous dinosaurs of different species were on the verge of extinction before the alleged asteroid, which led to the extinction of dinosaurs about 65.5 million years ago.
Scientists at the American Museum of Natural History revealed the disappearance of some groups of dinosaurs in the late Cretaceous period due to changes in the structure of their bodies.
The sudden impact of volcanic eruptions or asteroid wiped out the dinosaurs at the peak of their evolution? – Asks the author, Steve Brunet studies at Columbia University. – We found out that it was much more difficult, and perhaps asteroid catastrophe is not the main cause of extinction of the dinosaurs.

Previously, similar studies to evaluate the quantitative changes in species, but reports based on studies of fossils, can be misleading.

In the rocky areas of the fossils differ more diverse than in the great plains of America – explains Bruseytt. – In this study, we wanted to go further than simply count the number of species. ”

The team chose seven groups of dinosaurs, including nearly 150 species. Researchers found that the number of large herbivores, such as horned dinosaurs and probably permanently diminished in the late Cretaceous period.

At the same time, three types of dinosaurs have been a slight increase in biodiversity: some carnivorous predators, small herbivorous, the giant plant-eating dinosaurs ruminants.

However, the geographic location was the determining factor, as an example of massive shows that the North American territory of their number had decreased, while in Asia may have increased.

“Identifying these differences paints a detailed picture of the last 12 million years of dinosaur history, – the Bruseytt. – Contrary to popular belief, the latest Cretaceous period was not a static “lost world” that was suddenly destroyed by the asteroid impact.

Some dinosaurs were dramatic changes, and the number of large herbivorous dinosaurs continuously decreased over time, at least in North America. ”

Scientists believe that the study of fossils in North America may not be indicative of a global due to the large geological changes that have occurred there in comparison with other continents.

Therefore, unknown, survived the dinosaurs, if a collision with an asteroid did not happen.

“But at the same time, even if the population of dinosaurs or the local fauna declined, this does not mean that dinosaurs were doomed to extinction” – summed up Mark Norell, a professor of the Museum of Paleontology.

 
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Posted by on May 12, 2012 in Dinosaurs

 

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