Hulking reptiles were at a time when our planet collided with a celestial object, millions of years of evolutionary phase of decline. "The impact of an asteroid was only the final nail in their coffin," says lead researcher Manabu Sakamoto.
The causes of the collapse of the dinosaur population is said to be sought in other factors: the collapse of continental plates, constant volcanic activity and environmental selection pressures. For example dlouhokrcí sauropods, the giant herbivores, which included the popular brontosaurus, showed a steady gradual decline in numbers, which was after the asteroid impact just rapidly accelerated. Theropods, including Tyrannosaurus iconic, abruptly disappeared millions of years before the asteroid impact. Such a statement is a sharp contrast with the hitherto accepted theory that the dinosaurs 66 million years ago found at the very peak of their bloom.
This research, based on statistics and the fossil record, paleontologists have participated from the University of Reading and Bristol. Their conclusion is that for the last fifty million years ago the Earth said the collision with an asteroid of the dinosaurs best behind him. The main argument by those who experienced a low rate of speciation - the emergence of new species. Old dinosaur species from the fossil record is gradually disappearing and a new species is not a substitute for adequate pace. Far from it in all groups studied ancient lizards showed this trend is the same form, some perished gradually, others abruptly, as it was not enough to adapt to changed environmental conditions.
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"These results are really not expecting," he says and Manabu Sakamoto, leading a team of paleontologists. "Yes, asteroid impacts remains the first candidate as the cause of the final disappearance of the dinosaurs, but it is clear that from an evolutionary standpoint by that time long ago played prim." The Apocalypse including burning and dying vegetation, earthquakes, tsunamis, ubiquitous ash and eclipse the sky was therefore probably really happened, but much earlier than there was something that prevented the dinosaurs in the formation and evolution of new species. "Actually, dozens of millions of years before its final demise of the dinosaurs lost their dominant position on earth," says Sakamoto.
"Everything so far suggests that dinosaurs, which dominated terrestrial space for more than 150 million years, somehow lost the ability to adapt to further changes," says Mike Benton from Bristol University, coauthor of the study. "By their speciation slowed significantly, then they came the ability to cope with the impact of the environmental crisis after the asteroid impact. "Raisin in the sky caused by tons of ash in the atmosphere, leading to the death of vegetation. On the herbivorous dinosaurs they were dependent on them and they turn carnivorous. In their place, then they boarded the evolutionary changes in the environment much better prepared mammals. The paintings, which preceded ancient catastrophe, however, have a strong impact on the existing knowledge about nature conservation.
"Groups of animals that the accelerated rate of extinction facing their own, they are generally more vulnerable to total destruction if it takes place some catastrophic event," says Sakamoto. "Maybe when the current loss of biodiversity, extinction rates and the ongoing man-made climate change."
Author: Radomír Dohnal
Source: Ekolist.cz
