Scientists: Dinosaurs’ world domination after two mass extinctions
Experts say the giants took “at least 30 million years” to rule the planet and their rise to power came after they were twice nearly wiped out.
Professor Michael Benton and Steve Brusatte from the University of Bristol found that dinosaur domination was “a slow and complicated event, and driven by two mass extinctions”.
Brusatte, whose study is reported in Biology Letters, said: “The sheer size of dinosaurs like Tyrannosaurus makes us think there was something special about these animals that pre-ordained them for success right from the beginning.
“However, our research shows that the rise of dinosaurs was a prolonged and complicated process. It isn’t clear from the data that they would go on to dominate the world until at least 30 million years after they originated. It just wasn’t a case of dinosaurs exploding onto the scene because of a special adaptation. Rather, they had to wait their turn and evolved in fits and starts before finally dominating their world.”
Prof Benton said: “We argue that the expansion of the dinosaurs took up to 50 million years and was not a simple process that can be explained with broad generalisations.”
Dinosaurs originated 230 million years ago and survived the Late Triassic mass extinction 228 million years ago, when about 35% of all families died out.
It was their predecessors dying out during this extinction that allowed herbivorous dinosaurs to expand into the niches that had been left behind, the Bristol team said.
The team added that the rapid expansion of carnivorous and armoured dinosaur groups did not happen until after a much bigger mass extinction 200 million years ago, at the Triassic-Jurassic boundary.
At least half of the species now known to have been living on Earth at that time became extinct.
Historically, the rise of the dinosaurs has been treated as a classic case in which a group evolves key features that allow it to rapidly expand in numbers, fill many niches and out-compete other groups.
The research shows that dinosaurs evolved into all their “classic lifestyles” — such as big predators and long-necked herbivores — before they became abundant or diversified into the many species that we know today.
