Dinozorlar Tamamen Yok Olmadan Önce Sayıları Azalmaya Başlamış mıydı?

ever since the first dinosaurs on about two centuries ago people of all animals why did they go extinct when do they go extinct and we know that dinosaurs went extinct about 65 million years ago right at the end of the Cretaceous we know there was a big asteroid that hit the planet at that time we know there was massive volcanic eruptions going on at that time but it's remained a bit of a mystery did one or both of those things cause dinosaurs to go extinct or were there other factors involved we have a paper coming out in nature communications on the dinosaur extinction and how dinosaurs were changing during those 10 to 12 million years right before their extinction and this is a collaboration between myself and mark Norell my advisor here at the American Museum and our colleagues Richard Butler and Albert preto Marquez and Munich so what we've done with this project is we've looked specifically at dinosaur Anatomy there has been a lot of previous work on the dinosaur extinction over the last several decades but what most people have done before is they've looked at species towns they've looked at dinosaur diversity in terms of how many species of dinosaurs there were and how that changed over time what we do in this paper is that we take a completely different approach so we're not as interested in the number of species as we are in the number of kinds what we've done is we try to tease that signal out to look at the physical difference among different dinosaur species how that represents itself as one comes up to the terminal cretaceous event our results show really that the dinosaurs were in the state of flux during the the final 12 million years before they went extinct some groups of dinosaurs like the carnivorous dinosaurs and smaller species of plant eaters we're pretty steady in the revolution during those 12 million years before the extinction but other groups of dinosaurs specifically the very large plant-eating dinosaurs things like the ceratopsians like Triceratops and also the duck-billed dinosaurs these animals seem to have been undergoing a very long-term decline we also found that different dinosaurs living in different parts of the world we're changing in different way so dinosaurs living in North America generally seem to have been undergoing a decline in biodiversity at least these large plant eaters whereas those living in Asia seemed to have actually been increasing I think it will help us understand the extinction event a little better especially as the record becomes more densely sampled and were able to understand some different animal and organismal groups and to see if they show some of the same patterns as these groups of non-avian dinosaurs do we'll have a better picture of what was going on right before the big event