Dinosaurs were in decline as a species 50 millions years before the asteroid strike that finally wiped them out and the giants have their own success in dominating every terrestrial habitat to blame for the fall, says a study.
The migration of the dinosaurs across the globe was so rapid that it may have contributed to their demise, said the study published in the journal Nature Ecology and Evolution.
The speed of this expansion meant that the dinosaurs quickly became cosmopolitan and subsequently ran out of land. This lack of space then seriously impeded their ability to produce new species, eventually contributing to their decline, the research showed.
“They were perhaps too successful for their own good,” said Ciara O’Donovan, evolutionary biologist at the University of Reading in England and lead author of the study.
The study revealed the paths taken by the dinosaurs as they expanded out of South America during their rise to world dominance.
“The dinosaurs exploded out of South America in a frenzy of movement to cover the planet. It was during this time that diverse forms evolved and eventually led to species such as the fearsome Tyrannosaurus rex, Archaeopteryx (the earliest bird) and the gigantic, long necked Diplodocus,” O’Donovan said.
“This honeymoon period could not last forever though, and the dinosaurs eventually filled every available habitat on Earth. There was nowhere new for species to move to, which may have prevented new species from arising, contributing to the dinosaurs’ pre-asteroid decline,” O’Donovan said.
Fossil evidence shows dinosaurs originated in the late Triassic Period (around 230 million years ago) in South America, which was then part of the huge land mass called Pangea. This closely followed the world’s largest extinction event that wiped out almost all life on Earth.
The scientists developed a novel, statistical method to uncover where every dinosaur species’ ancestors existed, in three dimensional space, on the globe.
By doing this they were able to demonstrate that the dinosaurs spread unchecked across the huge available space, at a rate of 1,000 km/million years.
They dominated every terrestrial habitat, across all the continents as they drifted apart, over the course of 170 million years.
This saturation of the Earth caused the dinosaurs to become increasingly specialised to live in their existing environment, resulting in a fundamental change in the way they evolved and produced new species.
This curbed their progress and left them vulnerable to future changes in the environment, such as those caused by the asteroid strike, the study said.
