Sometimes it looks as if Therizinosaurus couldn’t have been real — as if Dr. Frankenstein sewed together parts from a hump-backed giraffe, a giant ground sloth and the X-Men character Wolverine to make one of the weirder dinosaurs of the Late Cretaceous.
“It’s really hard to picture how they made a living,” says James Kirkland, a state paleontologist with the Utah Geological Survey who studies these creatures.
But they did exist, for millions of years in the Cretaceous, and they were rather successful at doing so.
The Discovery of Therizinosaurus
The first fossils of Therizinosaurus were discovered in Mongolia’s Gobi Desert in the mid-20th century. At first, paleontologists didn’t know what to make of it — they thought it might be similar to a giant sea turtle, with long claws like the front arms of sea turtles today. The trouble was the area these fossils were found in would have been inland in the Late Cretaceous period.
Other bones from a dinosaur named Segnosaurus were discovered in subsequent years in the Gobi. These dinosaurs had long, thin necks and pointed beaks. They also had a pretty heavy torso. At first, researchers didn’t believe the Segnosaurus wasrelated to Therizinosaurus, but rather a missing link between theropods and sauropods.
“The group has bounced around a fair bit in some odd cubbyholes,” Kirkland says. “The Segnosaurs were a pretty bizarre group, no doubt about it.”
The whole Therizinosaurus group was assumed to be restricted to Asia until the discovery of North America fossils like Nothronychus, first described by Kirkland and his colleagues in 2001. Kirkland and his colleagues, including Lindsay Zanno, also described another dinosaur, Falcarius, that was likely one of the earliest in the Therizinosauridae family.
Zanno later gave clarity to the way the whole family was likely organized in evolutionary terms. Based on the fact they have been found in Asia and America, Kirkland says it’s likely that Therizinosauridae also lived in Europe, though none have yet been discovered there.
Read More: A Complete Dinosaur Timeline to Extinction: How Long Did They Roam Earth?
What did Therizinosaurus Eat?
Despite the fact they were theropods, paleontologists believed most Therizinosauridae were herbivorous, or at least omnivorous.
Many of the larger and later members of this family, like Therizinosaurus itself, may have fed similar to the way that giraffes do today – eating seeds, fruit, fresh buds or flowers off the tops of trees, Kirkland says. Therizinosaurus may have been up to 50-feet tall, and their toothless beats may have come handy in plucking food off of trees.
Kirkland speculates that the Therizinosauridae group really began to take off parallel to the rise of flowering plants in the Early Cretaceous. The early Falcarius could have likely lifted its arms above its head — an adaptation it may have used to pull down branches to feed more easily. As the Cretaceous went on, dinosaurs from this group got better at eating off trees.
Read More: The Time of Giants: How Did Dinosaurs Get So Big?
Why did Therizinosaurus Have Such Long Claws?
One of the standout features of Therizinosaurusare its crazy long claws, which stretched out more than 3 feet — among the largest of any land-living creature ever. This is likely one of the features that helped them make the cut for a feature in Jurassic World: Dominion. But the way the creature was portrayed in that movie wasn’t exactly accurate, otherwise.
It’s possible that Therizinosaurus may have used its long claws for defense, Kirkland says. A creature that waddled around “like a ground sloth” would have been an easy target for large predators such as Tarbosaurus, which was kind of the Asian stand-in for Tyrannosaurus Rex.
They may have used their long-clawed hands, which may have been surrounded at least partly by tissue, to slap threats, similar to the defensive strategies of giant anteaters. Their claws may have also been serrated, tearing flesh as they slashed an opponent.
Since they lived with such giant predators and apparently succeeded, “they can’t be that easy to kill,” Kirkland reasons.
Similar to Falcarius, it’s also possible that Therizinosaurus may have used their claws to help them feed on treetops, though Kirkland doesn’t necessarily see how this would have functioned.
Like most non-bird dinosaurs, Therizinosaurus met their end likely when the Chicxulub asteroid hit the Earth around 66 million years ago, drawing this strange evolutionary experiment to an end.
Read More: Two Asteroids May Have Wiped Out The Dinosaurs
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Joshua Rapp Learn is an award-winning D.C.-based science writer. An expat Albertan, he contributes to a number of science publications like National Geographic, The New York Times, The Guardian, New Scientist, Hakai, and others.
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