Therizinosaurus — the giant dinosaur with the longest claws of any known animal — used its three-feet-long, sickle-like talons for display, not combat, a study has found. Researchers from the University of Bristol and the Institute of Vertebrate Paleontology (IVPP) and Paleoanthropology in Beijing focussed on two groups of dinosaurs. These were the alvarezsaurs (160–66 million years ago) and therizinosaurs (139–66 Ma), both of whom had weird claws whose functions had previously been unclear.
In their study, palaeontologist Zichuan Qin of the University of Bristol and the IVPP and his colleagues used a computational biomechanics approach to identify the claws’ functions based on detailed comparisons with living animals.
From CT scans, the team recreated the claws in three dimensions, then modelled their ability to support different stresses using engineering methods.
While the giant claws of the therizinosaurus were found to be suitable only for display, those of their smaller cousins, the alvarezsaurs — which resemble rock picks — would have been suitable for digging.
Mr Qin said: “Our previous work has shown that alvarezsaurs evolved to become the tiniest dinosaurs by the end of the Cretaceous, and these dinosaurian midgets were using their punchy little claws for digging into ant hills and termite mounds. They were ant-eaters.
“Early alvarezsaurs, like Haplocheirus from the Jurassic, had multifunctional hands, but they were not good at digging. Their much smaller descendants had the efficient digging hands so they could feast on the Late Cretaceous termites.”
Paper author and palaeontologist Professor Michael Benton of the University of Bristol said: “Alvarezsaurs and therizinosaurs are definitely the strangest cousins among dinosaurs.
“Alvarezsaurs were the tiniest dinosaurs ever, the size of chickens with stubby forelimbs and robust single claws, but their closest relative, the therizinosaurs, evolved in the exact opposite path.”
Also involved in the research was Dr Chun-Chi Lao, an expert in therizinosaurs from the IVPP. He said: “Therizinosaurus is famous for its sickle-like claws, each as long as a samurai sword — Edward Scissor-hands on speed!
“We all saw Therizinosaurus in ‘Jurassic World’, hitting deer and killing the giant predator Giganotosaurus. However, this is unlikely.
“These long, narrow claws were too weak for combat. Our engineering simulation shows that these claws could not withstand much stress.”
Dr Lao continued: “Not all therizinosaur hand claws were so useless in combat… most other related species could use their claws as powerful hooking tools when feeding on leaves from the trees.
“So, we conclude that the largest claws of any animal ever were actually useless in mechanical function.”
Accordingly, he added, they “must have evolved under sexual selection to be used in display.
“The adult Therizinosaurus I guess could wave the claws at a competitor and effectively say, ‘look at me, back off’ or wave them around in some way like a peacock can use its tail in display to attract females for mating.”
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Paper co-author and dinosaur biomechanics expert Professor Emily Rayfield of the University of Bristol said: “Science and technology cannot bring dinosaurs back to life, but advanced computing and engineering techniques can show us how extinct animals lived.”
Such are especially useful, she added, “for extinct animals like alvarezsaurs and therizinosaurs, [which] are so bizarre that we can’t even find any living animals like them.
“This study shows very well how selection for function can lead to the emergence of specific, sometimes very bizarre, forms.”
The full findings of the study were published in the journal Communications Biology.
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