Meet The ‘Reaper Of Death,’ Tyrannosaurus Rex’s Older Cousin That Was Discovered In Canada

Published February 12, 2020
Updated March 9, 2021

Thanatotheristes degrootorum, "Reaper of Death" in Greek, is a tyrannosaur that lived about 79 million years ago, which pushes the tyrannosaur family's history back by about 10 million years.

Artist Rendering Of The Thanatos Degrootorum

Julius Csotonyi/The University of Calgary/Royal Tyrrell Museum/AFPThe jaw bones of this tyrannosaur species were found by a couple on a stroll in Alberta in 2008. It took nearly a decade for someone to thoroughly analyze them.

The Tyrannosaurus rex may be the king of the dinosaurs, but Canadian scientists have just discovered a new dinosaur species that might be its close, older cousin — and possibly the oldest member of the Tyrannosaurus family ever found in the northern latitudes of North America. Its name, Thanatotheristes degrootorum, translates from the Greek as “Reaper of Death,” making the discovery even cooler.

This behemoth trampled the plains of modern-day Canada around 79 million years ago. T. rex, meanwhile came along about 10 million years later and has been found all over North America.

As for the creature’s name, the researchers who discovered it primarily considered its place in the prehistoric food chain.

“We chose a name that embodies what this tyrannosaur was as the only known large apex predator of its time in Canada, the reaper of death,” said Darla Zelenitsky, assistant professor of Dinosaur Palaeobiology at the University of Calgary. “The nickname has come to be Thanatos.”

Reaper Of Death Dinosaur

Julius Csotonyi/The University of Calgary/Royal Tyrrell Museum/AFPThis artist rendering of the Thanatos’ head shows the vertical ridges, battle scars, and long deep snout. The latter was similar to that of the Daspletosaurus, suggesting this specimen filled some gaps in the tyrannosaur’s fossil record.

Oddly enough, the dinosaur’s fossilized bones were actually discovered in 2008 by Sandra and John De Groot, who were out for a stroll along a lakeshore in Alberta when they saw something poking up through the ice.

To their surprise, after joking that it looked like a dinosaur jaw, they discovered that’s exactly what it was.

“It was just kind of this ‘Wow’ moment of ‘Holy cow! You actually did find some teeth laying here on the ground,'” said Mrs. De Groot, a substitute teacher who’s collected bones and ammonites in the past.

Two years later, Donald Henderson, a paleontologist at the Royal Tyrrell Museum of Paleontology in Drumheller gave a talk at her school. She told him what she and her husband had found and offered to show him the remains and — after an enthusiastic meeting — the couple donated their find to the museum.

After that, it took researchers nearly a decade before anyone was able to take the bones out of storage and properly inspect them. Fortunately for Calgary University Ph.D. student Jared Voris, he turned out to be the one to do it.

He first noted that the long and deep snout was similar to the Daspletosaurus, indicating two separate tyrannosaur groups were represented in one specimen. The vertical ridges lining its upper jaw and battle scar were rather curious, too.

“The ridges were things that we had not seen before in another tyrannosaur, especially not another tyrannosaur from Alberta,” said Voris.

Alberta is renowned for an abundance of tyrannosaur fossils. From the Albertosaurus and Gorgosaurus to the Daspletosaurus and T. rex, the Cretaceous period’s most famous dinosaur family seem to lie buried just beneath the surface. Even with all those fossils, though, Thanatos is the first new tyrannosaur species found in Canada in 50 years.

The findings, published in the journal Cretaceous Research, explained that the deep, long snout was far more comparable to the tyrannosaurs unearthed in the southern United States than those found up north in Canada.

Experts believe this distinction in skull shape is likely due to dietary differences and the available prey.

“There are very few species of tyrannosaurids, relatively speaking,” said Zelenitsky. “Because of the nature of the food chain, these large apex predators were rare compared to herbivorous or plant-eating dinosaurs.”

Jaw Bones Of The Thanatos Degrootorum

Jared VorisThe upper and lower jaw bones of the “Reaper of Death” sat unexamined for years until graduate student Jared Voris took a stab at analyzing the species and genus.

The oval-shaped cheekbones, too, led the research team to designate the specimen as part of a whole new species. The find turns out to have additional significance as it pushes the markers of this dinosaur family’s place in history back by a few million years.

“Prior to the discovery, we knew all the most famous tyrannosaurs…were all coming from the last 10 or so million years of the Cretaceous,” said François Therrien, paleontologist at the Royal Tyrrell Museum.

“Now, with the new species, we’ve actually pushed back the record of tyrannosaurs.”

So, even though it went extinct no later than 66 million years ago, the new species can rest easy knowing it was given one of the cooler names in taxonomy.

After learning about the discovery of a new tyrannosaurus rex species named “Reaper of Death,” take a look at these 31 dinosaur facts and images that will blow your mind. Then, learn about the Nodosaur — the dinosaur mummy unveiled with its skin and guts intact.

Marco Margaritoff
A former staff writer for All That’s Interesting, Marco Margaritoff holds dual Bachelor's degrees from Pace University and a Master's in journalism from New York University. He has published work at People, VICE, Complex, and serves as a staff reporter at HuffPost.
John Kuroski
John Kuroski is the editorial director of All That's Interesting. He graduated from New York University with a degree in history, earning a place in the Phi Alpha Theta honor society for history students. An editor at All That's Interesting since 2015, his areas of interest include modern history and true crime.
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Margaritoff, Marco. "Meet The ‘Reaper Of Death,’ Tyrannosaurus Rex’s Older Cousin That Was Discovered In Canada.", February 12, 2020, Accessed June 25, 2024.