They discovered what was the first exclusively carnivorous animal that lived 42 million years ago

A saber-toothed tiger is for scientists the first truly carnivorous mammal in history

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A new article has described one of the first known cat-like predators on the west coast of North America, giving us new information about these ancient predators and the evolution of modern carnivores.

“Nowadays, the ability to eat a diet exclusively on meat, also called a hypercarnivore, is not uncommon. Tigers do it, polar bears can do it. If you have a domestic cat, you may even have a hypercarnivore at home. But 42 million years ago, mammals were barely figuring out how to survive on meat alone,” says paleontologist Ashley Poust of the San Diego Natural History Museum.

“A great advance was developing specialized teeth for cutting meat, which is something we see in this specimen just described,” says the scientist.

The newly described creature, called Diegoaelurus vanvalkenburghae, is known only for a part of the lower jaw with some attached teeth, but the teeth give a lot of information about this ancient predator.

Diegoaelurus vanvalkenburghae is part of the subfamily of extinct cats called Machaeroidinae, which means 'like a dagger'. This fossil appears to be the most recent machaeroidin found, and is very different from its closest known relative, Apataelurus kayi.

“Nothing like this has ever existed in mammals before,” Poust says.

“Some ancestors of mammals had long fangs, but Diegoaelurus and his few relatives represent the first feline approach to a meat diet, with saber-toothed front and sharp scissor teeth called carnassials on the back,” says the expert.

“It's a powerful combination that several groups of animals have evolved independently in the millions of years that have passed since then,” he adds.

The mandible of Diegoaelurus vanvalkenburghae. (San Diego Museum of Natural History) (San Diego Museum of Natural History)

It is important to note that other subfamilies have also developed saber-toothed predators, including the similarly named Machairodontinae, which contains Smilodon fatalis, the most famous saber-toothed cat.

The jaw has been in the museum's collection since 1988, but the team recently analyzed it. The fossil was unearthed from a 42-million-year-old bedrock called the Santiago Formation in San Diego. This formation dates back to the late Eocene and can give us information about a time when the world was warmer and California was a humid forest.

“The fossils of the Santiago Formation show us a wooded and damp California where tiny rhinos, primitive tapirs and strange herbivorous sheep-like oreodonts grazed under trees while unusual primates and marsupials clung to the upper canopy,” Poust said.

“This wealth of prey species would have been a heterogeneous mix for Diegoaelurus, allowing him to live the life of a specialized hunter before most other mammals,” he explained.

For now, this is the only fossil of Diegoaelurus, which makes it a bit lonely in the collection of the San Diego Museum, but as research progresses and further deepens, felines similar to this first carnivore could be discovered.