gorgonopsian skull
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Gorgonopsian skull. Credit: Kirstin Brink

Dinosaurs have something huge in common with mammals—like us—and it’s all in the teeth 

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Jan 1, 2021, 5:11 PM EST

Killer fangs and features that were reptilian and mammalian made gorgonopsians look like a dinosaur and a saber-toothed cat mashup that was never supposed to happen, possibly a reject from the Jurassic Park franchise.

Gorgonopsians were predatory proto-mammals that stalked the Earth 260 million years ago. They could have been mistaken for dinosaurs, but fossilized teeth from these bizarre synapsids have now revealed an unlikely parallel between dinosaurs and mammals, including humans. While gorgonopsians were more closely related to mammals than reptiles, their tooth structure was eerily similar to that of dinosaurs. The serrated knives they had for teeth were believed to be exclusive to dinosaurs until it was found that their meat-ripping teeth evolved way before dinosaurs ever did.

How gorgonopsians developed dinosaur teeth without dinosaur genes is an example of convergent evolution, which happens in unrelated species because of similar environmental conditions. These teeth were what made flesh-eating theropods into apex predators almost nothing could escape.

“The special arrangement of tissues in gorgonopsian and dinosaur teeth help to strengthen the serrations inside the tooth, making them last longer, which in turn lets the animal eat more efficiently,” Kirstin Brink, who recently coauthored a study published in Biology Letters, told SYFY WIRE. “The fact that this unique arrangement of tooth tissues evolved in distantly related lineages at different points in time means that this type of tooth must have been really good at gripping and ripping chunks of meat off of prey.” 

Millions of years before carnivorous dinosaurs made it to the top of the food chain, gorgonopsians were already there. They were originally overlooked because Brink thought there was no way anything else could have evolved such specialized teeth. She had previously done an exhaustive study of animals with ziphodont teeth, or teeth like blades with serrated edges in the front and back for maximum cutting potential. Almost nothing with these weapons in its mouth was left out, from modern sharks and Komodo dragons to prehistoric terrors like the proto-mammal Dimetrodon (which could also be easily mistaken for a dinosaur), saber-tooth cat Smilodon, and phytosaurs that could have passed for crocodiles.

L-R: gorgonopsian tooth, closeup of tooth serrations, and micro-scale images of the serrations. Credit: Kirstin Brink.

 

Brink also studied theropod dinosaurs like the aforementioned T. Rex and Allosaurus, along with Coelophysis, Carchadontosaurus, raptors, and Gorgosaurus, though the name of that last one is the only thing it has in common with gorgonopsians.

Every one of these ziphodonts had, or in the extant species, still has, the same microstructures in its teeth that made it such a successful predator. Blame it on the food chain and the constant struggle for survival. The complex way certain tissues are arranged in these types of teeth strengthens the serrations and gives them extra lasting power, which makes their bite fatal.

“I was surprised to find that these microstructures are also present in gorgonsopsians,” Brink said. “It’s one group I didn’t check in the original study, and shows that this tooth type was a feature of apex predators in different time periods, not just dinosaurs.”

When Brink took another look, she realized that gorgonopsid teeth evolved long before the oldest dinosaur specimen she had studied. Gorgonopsians went extinct at least 20 million years and up to 40 million years before ziphodont teeth appeared in the dinosaur Coelophysis. Not all serrated teeth are made alike. Both gorgonopsians and dinosaurs had two tissues, dentine and enamel, behind those deadly serrations. Strangely enough, Dimetrodon, which lived around the same time as gorgonopsians, and Smilodon, who appeared 2.5 million years ago, were related to them—serrated teeth and all—but lacking the tissue arrangement found in the teeth of the others.

This is where you get the connection to humans. Smilodon and Dimetrodon developed especially strong enamel for their teeth to hold up while tearing through and chewing meat, and this was eventually passed down to other mammals, including us. Brink ended up unintentionally connecting us to prehistoric monsters that were the furthest thing from homo sapiens.

“These teeth evolved first in apex predators of the synapsid lineage, and because of the similar way meat-eating dinosaurs bit and processed their food, they also evolved this tooth type,” she said.

Next time you look in the mirror, something that looks like a not-quite-dinosaur might stare back.