The dinosaur clade Maniraptora includes the ancestors of birds, and most maniraptoran dinosaurs used their hands for grasping and in flight, but early maniraptorans (alvarezsaurs and therizinosaurs) had extraordinary claws of mysterious function. University of Bristol paleontologist Zichuan Qin and colleagues developed a comprehensive methodological framework to investigate what the functions of these most bizarre bony claws are and how they formed.
Early maniraptoran dinosaurs, like alvarezsaurs and therizinosaurs, occupied enigmatic ecological niches and had bizarre morphological characters.
Alvarezsaurs underwent miniaturization to become the smallest non-avian dinosaurs ever, but with short, strong arms and hands with a stout, rock-pick-like, single functional finger.
Some therizinosaurs evolved large body sizes, with elongate fingers with slender and sickle-like unguals, sometimes over 1 m long.
“Alvarezsaurs and therizinosaurs are definitely the strangest cousins among dinosaurs,” said University of Bristol’s Professor Michael Benton.
“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.”
“Therizinosaurus is famous for its sickle-like claws, each as long as a samurai sword: Edward Scissor-hands on speed,” added Dr. Chun-Chi Liao, an expert on therizinosaurs from the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences.
“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.”
For their study, the authors developed a new, computational approach in biomechanics to identify functions based on detailed comparison with living…
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