Dinosaurs may have already been in decline before the asteroid strike that ended their reign on earth, says a new study.
Though dinosaurs are said to have gone extinct 65 million years ago, researchers at the American Museum of Natural History's paleontology division, have found that certain species may have already been close to disappearing.
"A lot of the time people think of the dinosaurs going extinct: 'oh, you know, an asteroid did it ... the dinosaurs were doing just fine, an asteroid came along and killed them all off'," said Steve Brusatte, a palaeontologist at the American Museum of Natural History, reported AFP.
"I think now we can say it was probably more complicated than that. You had some dinosaurs that were doing just fine, but you had others like these big plant eaters that were maybe in trouble."
The reserachers looked at a number of dinosaur sub-groups with over 150 land-dwelling species.
The researchers found, according to AFP, that horned and duckbilled dinosaurs were becoming less diverse before the asteroid, which indicates that the species was possibly in trouble.
Species that are thriving are often more diverse, a factor that increases survival rates.
According to Discovery News, this is the first study to examine the extinction of dinosaurs based on 'morphological disparity' - how their bodies varied in structure within particular groups.
Yet the researchers warn that declining diversity did not necessarily mean extinction
"Even if the disparity of some dinosaur clades or regional faunas were in decline during the terminal Cretaceous, this does not automatically mean that dinosaurs were doomed to extinction," read the study, said USA Today.
"After all, they note, "there are known instances in the fossil record in which major vertebrate clades endured catastrophic diversity and disparity losses, both during mass extinctions and normal background times, but later rebounded."
The study is found in the journal Nature Communications