by 
An “Absolutely Bizarre” dinosaur with claws so gigantic their function has long remained a mystery, they couldn’t use them to fight or fend off attackers because they were too weak, a new study has found.
theropod dinosaur, Therizinosaurus, lived in the late Triassic and Cretaceous periods (220 million to 66 million years ago). His scythe-like claws are in the latest “Jurassic world‘ film which features the beast knocking off a deer and impaling the wild predator Giganotosaurus. However, the new research shows that this representation is inaccurate.
“Movies and documentaries suggest they used these claws like long swords to fight each other or predators.” Zichuan Qin (opens in new tab), a PhD student at the University of Bristol in England who led the study, told Live Science. “But our research suggests that they cannot tolerate stress, meaning these animals could not use their claws to fight or defend themselves. The results surprised us all because we watched last year (Jurassic World) and everyone was amazed. We quickly realized: ‘No, that’s not true!’”
Therizinosaurs started out turkey-sized and grew to be 30 feet (10 meters) tall, about as tall as Tyrannosaurus rex. At the end of the Cretaceous, this “absolutely bizarre” feathered dinosaur looked “like a giraffe,” with short legs and a “huge butt” that it may have sat on and chewed leaves, the researchers said.
But what made this dinosaur a real eye-catcher were its narrow, 3-foot-long (1 m) “Edward Scissorhands” claws — the largest of any animal on record, according to the study.
Related: Dinosaur reaper with massive claws found in Japan
“There has been much debate as to what these claws were for, partly because they are so large and partly because they are attached to an animal whose other characteristics suggest it was herbivorous – their skulls and their teeth suggest that they were herbivores,” Paul Beret (opens in new tab)a paleobiologist at the Natural History Museum in London, who was not involved in the study, told Live Science.
Those disproportionately large claws were so weak they couldn’t even hook onto and pull down branches, according to the study, published Feb. 16 in the journal communication biology (opens in new tab). Researchers used detailed scans of fossils to create 3D computer models of the claws, which they tested for various mechanical functions, including digging, pulling and stabbing.
They also studied alvarezsaurs, a group of dinosaurs closely related to therizinosaurs that, unlike the latter, evolved into miniature dinosaurs with stone pick-like claws. “The alvarezsaurs became the smallest dinosaurs ever – smaller than a chicken,” Qin said. “Their claws were small but very strong and sturdy; they could withstand very heavy loads, like digging in the ground.”
The idea that Alvarezsaurus was a clawed anteater ideal for digging up anthills is widely accepted among paleontologists, but the new study offers more rigorous and quantitative support, Barrett said.
So why Therizinosaurus develop seemingly useless, gigantic claws? The researchers suggested that males display their long claws to attract females, much like peacocks unfurl their tails to impress potential mates.
“We conclude that they were mainly used for display,” co-author of the study Mike Benton (opens in new tab), professor of vertebrate paleontology at the University of Bristol, told Live Science in an email. “Therizinosaurs may flash and clatter their long claws to frighten others or to impress women.”
The authors presented a compelling case that rules out the use of these weak claws for combat, Barrett said. “However, they may have played a minor role in gathering food,” he added. “But very often in evolution it comes down to showing these very weird and complicated structures that look useless and who gets to mate with whom.”
He also suggested another possible purpose for the gigantic claws. “Maybe they even used them to groom each other. These animals were feathered, and for all we know they could have used them like elaborate combs.”
