Thousands of marine fossils reveal a rapid decline at the end of the Earth.
66 million years ago, the extinction event that wiped out all non-avian dinosaurs and countless other species caught the whole world in its grip. A new study published in the journal Nature Communications reveals that even the southernmost tip of the planet did not escape its effects.
Over a period of 6 years, researchers in the UK analyzed more than 6,000 marine fossils ranging in age from 69- to 65-million-years-old that had been collected from the Antarctic Peninsula. Everything from small snails to giant marine reptiles called mosasaurs was identified in what is one of the largest collections of marine fossils from the age of dinosaurs anywhere in the world.
Based on the layers of rock in which each specimen was found, the researchers were able to arrange the fossils by age. Right at the 66-million-year mark — coinciding exactly with the mass extinction at the end of the Cretaceous period — they observed a 65–70 percent reduction in the number of species living in Antarctica.
"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. Clearly, a very sudden and catastrophic event had occurred on Earth,” said James Witts, a doctoral student at the University of Leeds and lead author of the study, in a press release.
Though it has recently been proposed that the decline of the dinosaurs and other groups was gradual, the dinosaur fossil record is patchy and cannot compete with the scope of the marine fossil record.
"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," said Witts.
Scientists used to think that the organisms living in the polar regions were distant enough from the cause of the mass extinction to be adversely affected by it. Plants and animals in these regions also tend to be highly adaptable to extreme conditions, so it was assumed that they would have been resilient to the climatic changes that followed the asteroid impact.
This new study tells a very different story. “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," said study co-author Jane Francis from the British Antarctic Survey.
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