Paleontologists have discovered the fossilized remains of a bobcat-sized creature from a extinct lineage of carnivorous placental mammals.
Life reconstruction of Diegoaelurus vanvalkenburghae. Image credit: San Diego Natural History Museum.
Diegoaelurus vanvalkenburghae lived in what is now California, the United States, some 42 million years ago (Eocene period).
This ancient predator is part of Machaeroidinae, a taxonomically small group of carnivorous mammals that includes the earliest known saber-toothed mammalian carnivores. Their diversity is low, with only a handful of species described from North America and Asia.
“We know so little about Machaeroidines, so every new discovery greatly expands our picture of them,” said Dr. Shawn Zack, a paleontologist in the Department of Basic Medical Sciences at the University of Arizona College of Medicine and the School of Human Evolution and Social Change at Arizona State University.
“This relatively complete, well-preserved Diegoaelurus vanvalkenburghae fossil is especially useful because the teeth let us infer the diet and start to understand how Machaeroidines are related to each other.”
The fossilized remains of Diegoaelurus vanvalkenburghae were discovered in the 1980s in the Santiago Formation in San Diego County, southern California.
The specimen includes a lower jaw and well-preserved teeth, giving paleontologists new information about the behavior and evolution of some of the first mammals to have an exclusively meat-based diet.
“Today the ability to eat an all-meat diet, also called hypercarnivory, isn’t uncommon. Tigers do it, polar bears can do it. If you have a house cat, you may even have a hypercarnivore at home,” said Dr. Ashley Poust, a postdoctoral researcher in the Department of Paleontology at the San Diego Natural History Museum and the University of California Museum of Paleontology.
“But 42 million years ago, mammals were only just figuring out how to survive on meat alone.”
“One big advance was to evolve specialized teeth for slicing flesh — which is something we see in this newly described specimen.”
The jawbone of Diegoaelurus vanvalkenburghae. Image credit: San Diego Natural History Museum.
Diegoaelurus vanvalkenburghae was about the size of a bobcat, but with a downturned bony chin to protect its long upper saber teeth.
This animal and its relatives represent a sort of evolutionary experiment, a first stab at hypercarnivory — a lifestyle that is followed today by true cats.
“Nothing like this had existed in mammals before. A few mammal ancestors had long fangs, but Diegoaelurus vanvalkenburghae and its few relatives represent the first cat-like approach to an all-meat diet, with saber-teeth in front and slicing scissor teeth called carnassials in the back,” Dr. Poust said.
“It’s a potent combination that several animal groups have independently evolved in the millions of years since.”
The team’s paper was published in the journal PeerJ.
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S.P. Zack et al. 2022. Diegoaelurus, a new machaeroidine (Oxyaenidae) from the Santiago Formation (Late Uintan) of southern California and the relationships of Machaeroidinae, the oldest group of sabertooth mammals. PeerJ 10: e13032; doi: 10.7717/peerj.13032
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