Around 250 million years ago, before even dinosaurs had evolved, the Earth suffered an extended catastrophe so intense that every living organism felt its effects – and most of the planet's animals disappeared forever. Those that survived this Permian mass extinction were left in a world of broken ecosystems, facing an arduous road to recovery. But the creatures that managed to bounce back were quickly able to rise to dominance in a world of new opportunities.

Now, a toothy set of jaws unearthed in Nevada adds a surprising new piece to this story. The jaws' owner was a large carnivorous fish named Birgeria americana, an apex predator from a time when ecosystems weren't supposed to be recovered enough to support such predators at all – at least that's what scientists thought.

According to the international team of palaeontologists who studied and named the species, Birgeria was a pursuit hunter that would have reached an estimated two metres (six feet) in full-body length, and its mouth was suitably well armed with three different rows of teeth.

The 26-centimetre-long fossil preserving the right side of the skull of Birgeria americana. Image: UZH

The large size is significant: it means Birgeria would have been bigger than all of its earlier cousins. It seems this species was an early riser in the wake of extinction, evolving to top predator status before pretty much anything else had a chance.

But the big surprise about this fish is its age. The species comes from the very earliest Triassic Period, just about one million years after the Permian extinction. Animal remains from this time period – especially big ones – are extremely rare, and the world would have been a tough place to live.

"This surprising find from Elko County in northeastern Nevada is one of the most completely preserved vertebrate remains from this time period ever discovered in the United States,” said Carlo Romano of the University of Zurich, lead author of the new study.

An artist's reconstruction of the newly discovered predatory fish species Birgeria americana, with the fossil of the skull shown at bottom right. Image: Nadine Bösch

Most of the evidence from this period indicates that ocean food webs were severely disrupted. With so much life wiped out during the mass extinction, normal relationships between species were all out of whack, and it's thought to have taken several million years for ecosystems to recover (... and then the Age of Reptiles began!).

Some scientists have even wondered if the tropics – where Nevada was located at this time – were simply devoid of big animals altogether for a while, a phenomenon they called the "equatorial vertebrate eclipse".

These new finds, however, are teaching us that reality was a bit more complicated. Birgeria wasn't the researchers' only discovery: a bunch of other predatory fish from three different sites in Nevada were also unearthed, all around the same age. At least in this part of the world, it seems, food webs had already bounced back enough to support diverse and large carnivores – only one million years after the mass extinction.

The ability to study and understand how ecosystems respond after major extinction events is something uniquely offered by the field of palaeontology, and it's particularly important today, when stories of environmental tragedy make regular headlines. Birgeria americana isn't just a cool predator – it may also help us wrap our minds around what to expect as the planet continues to change around us.



Top header image: Nadine Bösch