Blood-Curdling Permian Monsters

Long before T. rex, the Earth was dominated by super-carnivores stranger and more terrifying than anything dreamed up by Hollywood.

The two animals circled each other, both assessing their rival's robust, hairless body. With sabre-teeth like steak knives, piercing claws and skin as thick as a rhino's, they snapped their jaws open nearly 90 degrees – and launched into battle. In a split second, it was over. Sinking its five-inch (12.7cm) canines into its opponent's boxy snout, like hot needles through wax, the attacker claimed victory. This actually happened – or something like it.

Around a quarter of a billion years later, on a sunny day in March 2021, Julien Benoit was handed a rather unpromising container and invited to take a look. He was working in a pleasantly cool office at Iziko Museum of Natural History in Cape Town, South Africa, where he had been invited to visit the university's fossil collections. The vessel was a very old, simple cardboard box.

"It hadn't been opened for at least 30 years," says Benoit, an associate professor of evolutionary studies at the University of the Witwatersrand, Johannesburg. Inside was a jumble of bones, including countless skulls, many of which had been mislabelled. As he was sorting through and re-classifying them – assigning them to long-extinct species – he noticed a small, shiny surface.

"It was an exciting moment. I immediately knew what I was looking at," says Benoit. With a wide smile, he went to visit his colleague and asked to borrow her microscope to take a closer look. The shiny surface belonged to a tooth. This one was pointy and rounded, and it was embedded in the skull of another animal, probably a member of the same species. Benoit believes that two wolf-sized individuals had been fighting for dominance before one of their smaller teeth snapped off.

But this wasn't a tooth from any dinosaur. It was an artefact of a long-forgotten world – one immortalised in stone long before T. rex, Spinosaurus or Velociraptor made their debut. The skull belonged to an unidentified species of gorgonopsian – a group of slick apex predators which stalked the Earth around 250 to 260 million years ago, chasing down large prey and ripping off chunks of their flesh to swallow whole.

This was the Permian, an obscure era of geological history where the planet was ruled by giant, bone-chilling beasts that ran with a characteristic waddle and sometimes snacked on sharks. During this living nightmare, there were occasionally more carnivores around than there were prey for them to eat on land.

A strange world

The Permian began some 299 to 251 million years ago, when all the land on Earth had coalesced into a single, rabbit-shaped lump – the supercontinent Pangaea – surrounded by a vast, global ocean called Panthalassa.

This was an era of extremes. It opened with an ice age that turned the southern half of the continent into a continuous block of ice and locked up so much water, global sea levels dropped by up to 120m (394ft). Once this was over, the supercontinent gradually warmed up and dried out. With such an expanse of continuous land, the interior did not benefit from the cooling or moistening effects of the ocean, creating swathes of wasteland. By the middle Permian, central Pangaea was mostly desert scattered with conifers, punctuated by the occasional flood. Parts were nearly uninhabitable, sometimes experiencing air temperatures of up to 73C (163F) – hot enough to slow-roast a turkey.

"So quite a lot of aridity, but nonetheless wetter down the edges, and certainly in the northern and southern hemispheres, there was plenty of vegetation," says Paul Wignall, professor of palaeoenvironments at the University of Leeds in the UK.

Then towards the end of the Permian, the entire planet abruptly heated up by about 10C (60F) – roughly double the worst case scenario today if greenhouse gas emissions continue to rise unchecked. This set the scene for the largest mass extinction in Earth's history, and the conditions in which the dinosaurs would come to thrive.

But during this era, the evolution of T. rex was still some way away. In fact, most of the iconic dinosaurs we're familiar with today were about as close to existing in the Permian as we are to their time now. Instead, the largest land animals were the synapsids – a peculiar group with a kaleidoscopic array of body shapes and features, from the newt-like Cotylorhynchus, with an oddly tiny head and the mass of a small moose, to the goofy Estemmenosuchus, reminiscent of a hippo wearing a lumpy papier-mâché party hat.

The synapsids shared their world with a variety of other eccentric wildlife. The skies were ruled by dragonfly-like insects, Meganeuropsis, the size of ducks. In fresh water, there were 33ft (10m)-long carnivorous amphibians to contend with – their long, snapping snouts resembling those of crocodiles. Meanwhile, the oceans were patrolled by mysterious shark-like fish with serrated circular "saws" attached to their mouths. It's thought that Helicoprion used their brutal apparatus to slice open the shells of ammonites and cut through the bodies of large, fast-moving prey.

"I mean, there were so many weird and wacky creatures… I think it just highlights what a vibrant time this was," says Suresh Singh, a visiting research fellow in the School of Earth Sciences at the University of Bristol in the UK. Indeed, this was the first time that four-legged animals had mastered living entirely on land. Before the Permian was the Age of Amphibians, when most species were still tied to water for at least part of their lives, Singh explains.

But synapsids had a major advantage over amphibians – they could incubate their young within their own bodies, or lay large eggs that retained their own moisture. They essentially had their own portable "private pond", so they no longer needed lakes or rivers to reproduce.

The group also developed waterproofing on their bodies, so they could live in a wide variety of environments. While some of the first synapsis had scales, others are thought to have had tough, naked skin. In general, they were slow-moving, cold-blooded animals – but they still found a way to get their claws on their favourite meal: meat.

- Author: Zaria Gorvett, BBC