Diegoaelurus was one of the first hypercarnivorous mammals

Even someone who’s put up with a hellcat would rather deal with hissing and furballs than a thing with knives for teeth and a craving for flesh.

Diegoaelurus vanvalkenburghae was not just a saber-toothed cat. It was also one of the first hypercarnivorous mammals, meaning meat was the only thing it ate (if its teeth are any indication). Its 42-million-year-old fossilized jawbone was just another specimen languishing in a museum drawer until paleontologists Shawn Zack, Ashley Poust and Hugh Weaver from the University of Arizona and San Diego Natural History Museum realize it belonged to a whole new species. . They co-authored a study recently published in Peerj. Poust realized that the jawbone belonged to a saber-toothed monster because its teeth gave it away.

“We know from sharp teeth that this animal was a committed meat eater and could not have survived without hunting,” she told SYFY WIRE. “It had serrations on its lower teeth, something that matches the serrations on large fangs and occurs in saber-toothed animals, as well as a huge bony frill, an extension of the chin to protect the saber-tooth when the jaw was closed.”

Although he must have looked feline, Diegoaelurus was not a real cat. It was a machaeroidine (machero- literally means knife-shaped). Their teeth stand out from those of cats, which evolved later, although there is some overlap. It is thought to be one of the first mammals to have been so dependent on meat that it would not have survived if it had not hunted. Now extinct, machaeroidines were the oldest mammals to have developed saber teeth, which were highly effective at biting thick-skinned ungulates, the predecessors of rhinos, tapirs and horses that existed in Eocene times. It may even have gone for some primates.

What Diegoaelurus had in common with existing felines is hypercarnivore. Some of the things you feed your cat may not be made entirely of meat, but without cat food and leftovers from the night before, felids are carnivores through and through. Just ask a tiger or a leopard.

This terror’s jaw (bottom left) was hiding in plain sight, but looking at its serrated teeth, there’s no doubt it was fierce. Instead of molars and premolars, it had carnivores on its back, blade-like and made to slice through unsuspecting prey. At the end of a stretch of empty space is the incomparable canine saber teething in front. The bridle on Diegoaelurus’ chin not only protected his murderous fangs, but accommodated the deep roots of his lower teeth, and this chin structure also gave him a strength boost so he could exert more biting force. on its prey.

Even without a complete skull (like the one in the Smilodon next to him in the photo above, which is the poster child of saber-toothed mammals), the teeth in that jawbone that identified him as a machaeroidine were enough to figure out that he would have had much larger saber teeth towards the front of his upper jaw. Imagine the jaws of Diegoaelurus being a smaller, but no less monstrous version of those of Smilodon. Its chin is also more pronounced, perhaps to help the small predator grab something twisting between its teeth. Smilodon only appeared 2.5 million years ago.

So how did adaptations like this evolve, and if cat-like creatures that displayed saber teeth were apex predators, why did they all die out? Having nothing alive to compare them to makes it difficult to find an answer. It is possible that their prey became extinct during the last Ice Age. This still does not explain why much older forms like Diegoaelurus disappeared.

“It is difficult to fully understand the pressures that lead to the evolution or extinction of saber-toothed animals, because we still don’t know exactly how they used these adaptations in their hunting, or even if they used them. all the same way,” Poust said.

Having nothing living to compare the Diegoaelurus fossil reveals the first evidence that different lineages of machaeroidines existed. Phylogenetic analysis revealed that it was definitely one of those fearsome creatures, since it was related to Apataelurus, which lived around the same time.

Macaeroidines did not prowl North America long after the arrival of Diegoaelurus. It is the last known species, and after its disappearance it would have been replaced by other extinct saber-toothed mammals known as nimravids.

Something else the discovery of Diegoaelurus did for paleontology besides the time gap between the disappearance of North American machaeroidines and the emergence of nimravids. There’s still a gap there, perhaps because there haven’t been many fossils found since that time, but that doesn’t necessarily mean that the machaeroidines were already extinct. It is possible that competition with the nimravids wiped them out.

Will sabertooth evolve again? Machaeroids and nimravids were saber-toothed pseudo-cats, and the carnivorous marsupials known as thylacosmilids also had serious fangs, but the saber-tooth disappeared with Smilodon. Even lions struggle with large prey and could use such an adaptation.

No living mammal now has saber teeth, although it may return to clouded leopards. This species may not be a machaeroidine, but it has some characteristics that would be similar.

“Who knows what the future holds for us?” said Poust. “If we create a world where big cats like the clouded leopard aren’t driven to extinction, then maybe one day we could have saber-toothed animals again.”

Helen L. Cuellar