Uploaded October 2025 | Updated September 2026, 2 weeks ago
We all know the classic prehistoric battle of T. rex vs Triceratops: the ultimate terrestrial carnivore against the freakishly agile sword-tank. That’s a fight that’s dominated the public perception of dinosaurs for over a hundred years, and for good reason. But what if I told you that Triceratops wasn’t the biggest herbivore that T. rex came into conflict with? Edmontosaurus annectens was a species of hadrosaurid that lived in the Late Cretaceous of North America, with the closely related Edmontosaurus regalis only being known from Canada. E. annectens is found in Canada as well as the northcentral United States. They were also incredibly successful animals, with thousands of disarticulated specimens known from the Ruth Mason Quarry in South Dakota. They were numerous, certainly, but their high population didn’t stop them from growing to be the size of elephants. A 2022 study found that an average fully-grown Edmontosaurus annectens would have weighed between five and six tonnes, and would be 11-12 meters long, using a sample size of over six hundred individuals. Of course, the maximum size is much larger, as you likely inferred from the title of this video. Two record-breaking specimens are known that are probably Edmontosaurus annectens: although if they turn out to be something different, they’d still be the biggest hadrosaurids known from North America by quite a bit. X-rex, or MOR 1142, is an enormous 7.5 meter tail that would scale to a 14.3 meter, 13+-tonne behemoth. The other specimen is a maxilla known as Becky’s Giant that would result in a broadly similar range, although the material is much worse. So we go from average African bush elephant size to bigger than a Columbian mammoth, with not a lot of specimens in between.
Soundtrack courtesy of Paleowolf
Thumbnail art by Emily Stepp and Joschua Knuppe
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We all know the classic prehistoric battle of T. rex vs Triceratops: the ultimate terrestrial carnivore against the freakishly agile sword-tank. That’s a fight that’s dominated the public perception of dinosaurs for over a hundred years, and for good reason. But what if I told you that Triceratops wasn’t the biggest herbivore that T. rex came into conflict with? Edmontosaurus annectens was a species of hadrosaurid that lived in the Late Cretaceous of North America, with the closely related Edmontosaurus regalis only being known from Canada. E. annectens is found in Canada as well as the northcentral United States. They were also incredibly successful animals, with thousands of disarticulated specimens known from the Ruth Mason Quarry in South Dakota. They were numerous, certainly, but their high population didn’t stop them from growing to be the size of elephants. A 2022 study found that an average fully-grown Edmontosaurus annectens would have weighed between five and six tonnes, and would be 11-12 meters long, using a sample size of over six hundred individuals. Of course, the maximum size is much larger, as you likely inferred from the title of this video. Two record-breaking specimens are known that are probably Edmontosaurus annectens: although if they turn out to be something different, they’d still be the biggest hadrosaurids known from North America by quite a bit. X-rex, or MOR 1142, is an enormous 7.5 meter tail that would scale to a 14.3 meter, 13+-tonne behemoth. The other specimen is a maxilla known as Becky’s Giant that would result in a broadly similar range, although the material is much worse. So we go from average African bush elephant size to bigger than a Columbian mammoth, with not a lot of specimens in between.
Soundtrack courtesy of Paleowolf
Thumbnail art by Emily Stepp and Joschua Knuppe
Join this channel to get access to perks:
youtube.com/channel/UCmkkmzfWWf4HzrO8SGO3gjw/join
