New evidence supports asteroid theory of dinosaur extinction


The poles were no safer than the rest of the planet when the bell tolled for the dinosaurs, new research suggests. Amy Middleton reports.


Marine giants such as the Mosasaurus vanished just as suddenly as everything else.
CHRIS BUTLER/GETTY IMAGES
There was no escaping the extinction event for the dinosaurs, not even at the planet’s poles, according to new research that supports the theory of an asteroid strike being the culprit.

A study of 6,000 Antarctic fossils suggests dinosaurs there lived no longer than those in the rest of the world.

The reason for the mass prehistoric extinction is still debated – however, the researchers say their new finding supports the hypothesis that the dinosaurs were wiped out by the impact of an enormous asteroid, rather than environmental changes due to volcanic activity.

Previously, many believed the ordeal was far enough away from the world’s poles that dinosaurs in those areas survived longer than others. It was thought that polar dinosaurs might be better equipped to deal with dramatic changes in environment, due to their experience through months of darkness and low food supply.

But new research – and one of the biggest fossil studies of its kind – refutes these theories.

An international team of researchers studied a collection of 6,000 marine fossils, lifted from Seymour Island on the Antarctic Peninsula, dating between 69 and 65 million years old.

'One day everything was fine – the Antarctic had a thriving and diverse marine community – and the next, it wasn’t.'

The findings, published this week in Nature Communications, show a steep reduction of around 70% of species living in the Antarctic, which took place 66 million years ago, at the end of the Cretaceous Period – the same time as species declined around the rest of the world.

“Our research essentially shows that one day everything was fine – the Antarctic had a thriving and diverse marine community – and the next, it wasn’t,” explains lead author James Witts from the University of Leeds.

“Clearly, a very sudden and catastrophic event had occurred on Earth.”

Among the fossils were marine giants Diplomoceras, with its paper-clip-shaped shell, and Mosasaurus, which makes a cameo in Jurassic World, along with smaller species such as clams and snails.

This rapid and intense decline in species suggests that a sudden event caused the extinction of the dinosaurs, rather than a gradual change in environment, the researchers say.

“This is the strongest evidence from fossils that the main driver of this extinction event was the after-effects of a huge asteroid impact, rather than a slower decline caused by natural changes to the climate or by severe volcanism stressing global environments,” says Witts.

The study is particularly significant for its abundance of fossils, says co-author Jane Francis from the British Antarctic Survey.

“These Antarctic rocks contain a truly exceptional assemblage of fossils that have yielded new and surprising information about the evolution of life 66 million years ago,” says Francis.

“Even the animals that lived at the ends of the Earth close to the South Pole were not safe from the devastating effects of the mass extinction at the end of the Cretaceous Period.”

Marine fossils tend to be particularly abundant and high quality because the undersea environment offers ideal conditions for preserving.

“Most fossils are formed in marine environments, where it is easy for sediment to accumulate rapidly and bury parts of animals, such as bones, or bodies of creatures with a hard shell,” Witt explains.

“This means that marine fossils are generally much more abundant. They can give us a much larger data set for studying how ecosystems and biodiversity change over time in the geological past, and enable us to draw robust conclusions about events during periods of rapid environmental change, like mass extinctions.”

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Amy Middleton is a Melbourne-based journalist.