Dinosaurs were becoming extinct well before an asteroid struck the Earth, wiping them out, according to a new study.
Researchers from the University of Reading in England said dinosaurs were already on a decline for at least 50 million years before an asteroid exterminated them.
Although the decline was slow, "it is clear that (dinosaurs) were already past their prime in an evolutionary sense," lead researcher and paleontologist Dr. Manabu Sakamoto said.
To come to that conclusion, researchers used fossil records and statistical analysis.
BBC News reported that a study from 2014 indicated that only some species were in decline, not all dinosaurs.
That same study showed that the decline began only a few million years before the asteroid strike.
CNN reported that the latest research found that all dinosaurs were on the decline, regardless of species.
Long-necked giant sauropod dinosaurs were declining the fastest, followed by theropods, whose decline was gradual. Theropods include the Tyrannosaurus rex.
"All the evidence shows that the dinosaurs, which had already been around, dominating terrestrial ecosystems for 150 million years, somehow lost the ability to speciate fast enough," Professor Mike Benton of the University of Bristol, one of the co-authors, said in a news release.
The researchers hope that the results of the study provide insight into biodiversity in the future.