You know, until that whole asteroid thing.
Most paleontologists agree that the Chicxulub asteroid impact, possibly coupled with intense volcanic activity, wiped out non-avian dinosaurs (all dinosaurs except birds) at the end of the Cretaceous period, approximately 66 million years ago.
However, there is debate about whether dinosaurs were flourishing or whether they had already been in decline due to climate change. A new study that modeled the changing environment and dinosaur species distribution in North America suggests that dinosaurs were likely not in decline before the Chicxulub strike.
According to the study, dinosaurs as a whole were adaptable animals, capable of coping with the environmental changes and climatic fluctuations that happened during the last few million years of the Late Cretaceous. It suggests previous analyses have underestimated the number of species at the end of the Cretaceous period.
During the Cretaceous, North America was split in two by a large inland sea. In the western half there was a steady supply of sediment from the newly forming Rocky Mountains, which created good conditions for fossilizing dinosaurs once they died. The eastern half of the continent was characterized by conditions far less suitable for fossilization.
This means that far more dinosaur fossils are found in the western half of North America, and this fossil record is often used to suggest dinosaurs were in decline during the few million years before the asteroid strike.
However, instead of using the fossil record exclusively, the researchers employed ‘ecological niche modeling.’ This approach models which environmental conditions, such as temperature and rainfall, each species would need to survive. The scientists then mapped where these conditions would occur across the continent over time.
This allowed them to create a picture of where groups of dinosaur species could survive as conditions changed, rather than just where their fossils had been found. The team found habitats that could support dinosaur groups were actually more widespread at the end of the Cretaceous period, but that these were in areas less likely to preserve fossils.
The findings appear in the journal Nature Communications.