Ancient Finned Predator Feasted on Sharks

According to the history books, five mass extinctions have devastated the planet since it formed 4.6 billion years ago.

But history may have to be rewritten after the discovery of fossils that point to a sixth mass extinction taking place 260 million years ago.

Most researchers blame either the Earth's warming climate or the arrival of humans on the islands for the mammoth's demise, he said.

But pygmy mammoths likely survived a steamier, more severe climate swing about 125,000 years ago. "This new find suggests they had to have lived during a period even warmer than the present," Muhs told Live Science.

Doubters of the Alvarez hypothesis don’t question the ‘smoking gun’ evidence that an impact happened near the end of the Cretaceous, but they don’t think it was the main cause of the extinctions.

When Roy Plotnick thinks about species going extinct, he tries to envision how that might look to a scientist millions of years from now. Plotnick, a palaeontologist at the University of Illinois at Chicago, has launched an unusual thought experiment to consider whether animals that vanish today might never be represented in the future fossil record. He calls it the 'invisible extinction'.

Plotnick sat down with Nature this week at a Geological Society of America meeting in Vancouver, Canada, where he put these ideas forward.