The fossil of a cat-like mammal that lived between 37 and 40 million years ago has revealed that a group of sabre-toothed carnivores, the nimravids, evolved into diverse species much earlier than thought.
Animals with sabre-like teeth have arisen over and over again during the past 66 million years, but the nimravids, which eventually evolved into a range of sizes from modern-day bobcat (or red lynx) to lion, were among the most fearsome.
at the San Diego Natural History Museum in California and his colleagues have now identified a new species, named Pangurban egiae, from fossils salvaged from a construction site in San Diego in 1997. The first part of the name is a reference to a 9th-century poem written in Old Irish that likens a cat’s pursuit of prey to the academic quest for truth, while the second honours palaeontologist Naoko Egi.
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The fossils were originally categorised as a hyena-like mammal species, but now the team says they are actually one of the oldest examples of a nimravid yet found in North America.
Poust and his colleagues estimate that P. egiae roamed a forest in what is now San Diego between 37 and 40 million years ago, shortly after nimravids first arose. The carnivore’s age means it is about as old as another nimravid, Maofelis cantonensis from China, raising questions about whether these cat-like predators evolved in North America or Eurasia first.
Despite being an early member of its family, the anatomy of P. egiae resembles that of nimravid species that prowled North America millions of years later. “It’s interesting that this early-appearing species displays such advanced features,” says at the North Dakota Department of Mineral Resources. Finding a developed nimravid from early in the group’s history hints that there are others awaiting discovery. “By extending the time that nimravids were in North America,” says Poust, “I think it does indicate a bevy of unknown meat-eating relatives.”
Regardless of which continent they arose on, the sabre-toothed nimravids may have evolved during a time when global climate change was altering landscapes across the planet. “Warm and wet forested landscapes transitioned to more open savannahs with pronounced seasonal wet and dry cycles,” says Boyd, which resulted in small prey such as primates becoming more scarce and larger prey becoming more common. Early nimravids may have taken advantage of these changes, perfecting their pounces as some of the world’s most successful sabre-tooths.
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