The dinosaurs were already doomed long before the meteorite hit, scientists find

"Don't cry for me, I'm already dead."

A new study has revealed that certain dinosaur species were in decline millions of years before the meteorite that's credited for wiping most of them out smashed into Earth.

That's a pretty huge deal, because the results could finally put an end to one of the longest-running debates in palaeontology, and help us understand once and for all what happened in the final years of the non-avian dinosaurs on Earth.

To figure out what happened, Venditti and his team used statistical analysis and fossil record data to create a family tree of the three main types of dinosaurs: the ornithischians (beaked herbivores), theropods (carnivores such as T. rex), and sauropods (long-necked plant-eaters).

They found that while dinosaurs began to flourish during the late Triassic period around 220 million years ago, certain species began dying off faster than they could be replaced around 100 million years later.

That's tens of millions of years before the 9.6-km Chicxulub meteorite hit Earth.

Prior to this research, many scientists thought that dinosaurs had been flourishing up until then. But this study suggests that the group was actually in a long-term decline - and that could have been what made them so susceptible to being wiped out.

What scientists think right now is that when the Chicxulub meteorite hit Earth 66 million years ago, it threw millions of tonnes of dust up into the atmosphere, blocking the Sun's rays and causing short-term cooling and widespread plant die-off.

But while the majority of the dinosaurs couldn't survive those changes, other species, such as the mammals, managed to eventually bounce back.

The team suggests that the weakening dominance of the dinosaurs before the impact could have given mammals the edge to endure the asteroid impact.

The study can also help us predict groups of animals alive today that will be particularly vulnerable to extinction - namely those that are losing species faster than they can replace them.

But there's still one question that everyone's dying to know: does this study mean that dinosaurs would have gone extinct anyway, regardless of the meteorite?