Alvarezsaurs claws when digging dirt. Credit: Shuyang Zhou for the 3D modeling and functional scenario restoration
The claws of dinosaurs had many functions, but a team from the University of Bristol and the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in Beijing has now demonstrated that some predatory dinosaurs used their claws for digging or even for display purposes.
The study, which centered on two groups of theropod dinosaurs – the alvarezsaurs and therizinosaurs – aimed to uncover the mystery surrounding their peculiar claws. The findings revealed that the rock-pick-like claws of the alvarezsaurs were utilized for digging, while their close relatives, the giant therizinosaurs, used their overgrown, meter-long, sickle-shaped claws for display purposes.
The new work is led by Zichuan Qin, a Ph.D. student at the University of BristolThe University of Bristol, a red brick research university in Bristol, England, received its royal charter in 1909. However, it can trace its history back to 1876 (as University College, Bristol) and 1595 (as Merchant Venturers School). It is organized into six academic faculties composed of multiple schools and departments running over 200 undergraduate courses.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>University of Bristol and the IVPP. He developed a new, computational approach in biomechanics to identify functions based on detailed comparison with living animals. First, the claws were modeled in three dimensions from CT scans, then modeled for stress and strain using engineering methods, and finally matched to functions of pulling, piercing, and digging by comparison with modern animals whose claw functions are known.
Therizinosaurs claws hooking and pulling trees. Credit: Shuyang Zhou for the 3D modeling and functional scenario restoration
“Alvarezsaurs and therizinosaurs are definitely the strangest cousins among dinosaurs,” said Professor Michael Benton, one of Zichuan’s supervisors. “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. We all saw Therizinosaurus in ‘JurassicThe Jurassic period is a geologic time period and system that spanned 56 million years from the end of the Triassic Period about 201.3 million years ago to the beginning of the Cretaceous Period 145 million years ago. It constitutes the middle period of the Mesozoic Era and is divided into three epochs: Early, Middle, and Late. The name "Jurassic" was given to the period by geologists in the early 19th century based on the rock formations found in the Jura Mountains, which were formed during the Jurassic period.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>Jurassic World’ hitting deer and killing the giant predator Giganotosaurus. However, this is unlikely. These long, narrow claws were too weak for combat.” said Dr. Chun-Chi Liao, an expert on therizinosaurs from IVPP who co-authored this study. “Our engineering simulation shows that these claws could not withstand much stress.”
“Not all therizinosaur hand claws were so useless in combat, but most other related speciesA species is a group of living organisms that share a set of common characteristics and are able to breed and produce fertile offspring. The concept of a species is important in biology as it is used to classify and organize the diversity of life. There are different ways to define a species, but the most widely accepted one is the biological species concept, which defines a species as a group of organisms that can interbreed and produce viable offspring in nature. This definition is widely used in evolutionary biology and ecology to identify and classify living organisms.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>species could use their claws as powerful hooking tools when feeding on leaves from the trees,” Dr. Chun-Chi Liao added, “so, we conclude that the largest claws of any animal ever were actually useless in mechanical function, and so 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.”
Key taxa and work pipeline use in this paper. Silhouettes show the large and elongated forelimb of the late-branching therizinosaurian Therizinosaurus (a) and the overall body shape and highlighted forelimb of the late-branching alvarezsauroid Mononykus (b), scaled against an adult human (height ~1.8 m). The work pipeline demonstrated by an ungual model from the Jurassic alvarezsauroid Haplocheirus, includes processes of 3D model reconstruction (c); model smoothing, measurement, and morphological analysis (d); finite-element analysis, ‘intervals’ method and functional-space analysis (e); and total evidence functional assessment (f). Credit: Zichuan Qin
“Our previous work has shown that alvarezsaurs evolved to become the tiniest dinosaurs by the end of the CretaceousThe Cretaceous is a geological period that lasted from about 145 to 66 million years ago. It is the third and final period of the Mesozoic Era. It ended with the Cretaceous–Paleogene extinction event.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]”>Cretaceous, and these dinosaurian midgets were using their punchy little claws for digging into ant hills and termite mounds. They were ant-eaters,” said Zichuan Qin.
“Our study shows that the 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,” added Zichuan Qin.
“Science and technology cannot bring dinosaurs back to life, but advanced computing and engineering techniques can show us how extinct animals lived,” said Professor Emily Rayfield, one of Zichuan’s supervisors, and an expert of dinosaur biomechanics. “Especially for extinct animals like alvarezsaurs and therizinosaurs, they are so bizarre that we even can’t find any living animals like them. Luckily, advanced technology can help us to simulate, on a computer, the functioning of extinct animals using fundamental engineering and biomechanical principles. This study shows very well how selection for function can lead to the emergence of specific, sometimes very bizarre, forms.”
Reference: “Functional space analyses reveal the function and evolution of the most bizarre theropod manual unguals” by Zichuan Qin, Chun-Chi Liao, Michael J. Benton and Emily J. Rayfield, 16 February 2023, Communications Biology.
DOI: 10.1038/s42003-023-04552-4
Source: SciTechDaily
