Photo by Elvis Barukcic/AFP/Getty Images.
The dinosaurs may not have been quite as care-free as we thought before their extinction.
A new study by American and German scientists published this week suggests that some dinosaurs may have already been in decline before a space rock collision with earth ended their reign some 65 million years ago.
As the AFP notes, the research doesn't dispute the cause of the mass-extinction event. The findings do indicate, however, that large herbivores, especially horned and duckbilled herbivores, were becoming less diverse during the last stages of the Cretaceous, at least in North America. As Discovery News explains, greater diversity is generally considered to indicate a healthier population.
Medium-sized herbivores, along with carnivorous dinosaurs, however, were thriving at the time of extinction. The reason for the selective decline is unknown, but most likely ecological.
There's some debate over the significance of the study's findings. Stephen Brusatte, a graduate student affiliated with the study interviewed by Discovery said that the findings are debatable, but the study challenges a notion that the dinosaurs lived a static existence before extinction and were wiped out in their prime.
Paul Upchurch, a University College London paleobiologist, meanwhile, told the science outlet that the "study could actually be taken as evidence in favor of a sudden extinction," adding that the findings could simply be "evolutionary business as usual."