Dinosaur extinction event was deadly for Antarctic life

The mass extinction event that killed the dinosaurs was sudden and just as deadly to life in the polar regions, according to a study of more than 6,000 marine fossils from the Antarctic.
The research involved a six-year process of identifying more than 6,000 marine fossils ranging in age from 69- to 65-million-years-old that were excavated by scientists from the University of Leeds in the UK and the British Antarctic Survey on Seymour Island in the Antarctic Peninsula.
This is one of the largest collections of marine fossils of this age anywhere in the world. It includes a wide range of species, from small snails and clams that lived on the sea floor, to large and unusual creatures that swam in the surface waters of the ocean.

With the marine fossils grouped by age, the collection shows a dramatic 65-70 per cent reduction in the number of species living in the Antarctic 66 million years ago - coinciding exactly with the time when the dinosaurs and many other groups of organisms worldwide became extinct at the end of the Cretaceous Period.
"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 James Witts, a PhD student in the University's School of Earth and Environment.

The study is the first to suggest that the mass extinction event was just as rapid and severe in the polar regions as elsewhere in the world.

Previously, scientists had thought that organisms living near the Poles were far enough away from the cause of the extinction to be badly affected - whether this was an asteroid impact in the Gulf of Mexico, where a giant buried impact crater is found today, or extreme volcanism in the Deccan volcanic province in India.
It had also been proposed that animals and plants in the polar regions would have been more resilient to global climatic changes as a result of living in environments that were always strongly seasonal.

For example, life near the Poles has to adapt to living in darkness for half of the year and to an irregular food supply.
"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 Jane Francis from the British Antarctic Survey.
While some previous studies have suggested that the demise of the dinosaurs and other groups was gradual, many scientists argue that the dinosaur fossil record in particular is patchy, and cannot compete with marine fossils in terms of quantity and biodiversity.

The study was published in the journal Nature Communications.