Science & Tech

New Tyrannosaur Species Found, Dubbed ‘Reaper of Death’

by Matthew Hart
Feb 11 2020 • 8:00 AM

Everybody’s favorite serial killer is back, and no, we’re not talking about Dexter (seasons one-four). We’re talking about the ultimate killing machine that was a tyrannosaur. But this time, a new species of the “Tyrant Lizard” has popped up, and it’s been awarded the deadly moniker, Thanatotheristes degrootorum, or Reaper of Death. It was also found in Canada.


National GeographicOpens in a new tab reported on the discovery of the new species of tyrannosaur, which was made by Jared Voris, a current PhD student at the University of Calgary. Voris et al. recently announced the discovery in the journal, Cretaceous ResearchOpens in a new tab, but the actual finding of the fossilized bones happened in 2010, when farmer and “paleontology enthusiast,” John De Groot discovered them while hiking near Hays, Alberta. Hence the new species’ full name, Thanatotheristes degrootorum. (ThanatotheristesOpens in a new tab, the genus name, comes from combining Thanatos, the Greek god of death, with, theristes, which is an ancient Greek word for “one who reaps or harvests.”)

New Tyrannosaur Species Found, Dubbed ‘Reaper of Death’_1

An approximate location of where De Groot discovered the T. degrootorum fossils. Google Maps 

It seems that Voris wasn’t expecting to find a new species of tyrannosaur, but rather stumbled across it as he was cataloging fossils at the Royal Tyrrell MuseumOpens in a new tab. According to CTV NewsOpens in a new tab, Voris spent years cataloging tyrannosaur bones at the Royal Tyrrell Museum for his masters, and at one point came across the bones discovered by De Groot. Voris says that he thought the bones seemed unique because of the vertical ridges that run the length of the upper jaw.


Those vertical ridges along the upper jaw, which look like gnarly scars made of bone in the above illustration of T. degrootorum—as well as all of the other, apparently significant yet still esoteric physical differencesOpens in a new tab such as a “rounded and inflated orbital margin of the jugal”—is what sets the new species apart from others belonging to the family, Tyrannosauridae.

For context, T. degrootorum was much smaller than T. rex. While paleontologists suspect that T. degrootorum was about 26 feet long based on the skull De Groot found, the most complete T. rex specimens ever found max out at 40 feet in lengthOpens in a new tab. T. degrootorum was also around long before T. rexOpens in a new tab ever roamed the Earth: the former species lived around 80 million years ago, while the latter was out there scaring the “droppings” out of other prehistoric creatures around 66 million years ago.


Moving forward, Voris and the other scientists studying T. degrootorum‘s fossilized skull hope to glean more information about how the relatively small species, and other ones like it belonging to the same family, evolved into the monster tyrannosaurusesOpens in a new tab we’re now generally more familiar with. T. degrootorum may also help researchers to better understand why tyrannosauruses split off into two distinct lineages over time in North America, with a northern group developing long, deep snouts, and a southern group developing significantly shorter snouts.

What do you think about this new “Reaper of Death” species of tyrannosaur? Do you think it really deserves the name “Reaper of Death,” or should a name that aggressive be reserved for one of the larger species of the Tyrannosauridae family? Dust off any buried feelings you may have on the topic in the comments!

Feature image: Julius Scotonyi / the Royal Tyrrell Museum of PalaeontologyOpens in a new tab