Australian scientists say almost half of all dinosaur species were already extinct before the asteroid event because the climate was too cold for them
It is possible that the dinosaurs could not cope with climatic changes. An increasing cold wiped out most of the dinosaurs even before the asteroid that gave them the death blow. That's what scientists say. The asteroid that struck 65 million years ago during the Cretaceous period, was apparently the factor that finally eliminated what nature had started earlier.
However, Australian scientists say that almost half of all dinosaur species were already extinct by then, because the climate was too cold for them. Fossil evidence from the Drumheller Valley in Alberta, Canada, covering seven million years before the asteroid hit, shows that the average temperature in that area dropped from 25 degrees to about 15 degrees.
Many cold-blooded lizards such as crocodiles, turtles, as well as many herbivorous dinosaurs died out as a result of the cooling climate.
Readings of the oxygen isotopes from the fossils show that the temperature at which they formed changed over time. They found that there was a decrease in rainfall during the period when many species became extinct.
However, David Ebert from the Royal Museum of Paleontology in Tyrrell, who headed the study, said that it is not clear why the dinosaurs were so affected.
Dr. Angela Milner, head of palaeontology at the Natural History Museum in London, said that this claim was quite common, but the current study using the isotope records shows unequivocally that there was a significant drop in temperature."
According to Dr. Milner, warm-blooded dinosaurs could tolerate low temperatures for a short time because their large bodies could maintain a constant temperature. However, they will not be able to survive in the long term. "The popular opinion today is that they became extinct because of the asteroid, however the fossil evidence does not support this version in the way that people would like to think, but it is possible that the asteroid delivered the "punch blow".
