Tech UPTechnology'Therizinosaurus': the scythe dinosaur from Jurassic World Dominion

'Therizinosaurus': the scythe dinosaur from Jurassic World Dominion

In the Jurassic World: Dominion trailers Extraordinary creatures continue to appear that we had not seen in any previous installment. Among them stands out a huge dinosaur, fully feathered, with a mouth ending in a strong beak, and with a striking feature: three huge claws on each front leg, shaped like a scythe claw.

Fossil claws of Therizinosaurus are more than 70 meters long.centimeters each . If you add the keratin covering, which would surely have been lost during fossilization, the claw in life probably measured more than a meter. This feature makes Therizinosaurus the animal with the longest claws known . However, very few remains of this fossil species exist, and most of what is inferred is by anatomy compared to other animals in the same group.

scythe lizard claw

The first fossils of Therizinosaurus cheloniformis are found in 1954 by Soviet paleontologist Evgeny Maleev. The large claw gives the genus its name: from the Greek θερίζω, therízo , meaning scythe. The specific epithet tells us, however, “similar to a turtle” . And it is that, due to the first remains found, Maleev thought that he was facing an animal of these characteristics, which would use its enormous claws to harvest algae.

Almost 20 years must have passed before Therizinosaurus ceased to be classified as a turtle, to be considered a dinosaur, specifically from the group of theropods —the same to which Tyrannosaurus or Velociraptor belonged—. This designation was reinforced by the discovery of new remains, which included part of the arm and several ribs.

In 1979 Segnosaurus was discovered. The remains of this animal, although very fragmented, were more complete than those of Therizinosaurus : the lower jaw, neck vertebrae, pelvis, part of a hind leg, almost complete tail, and most importantly, part of a arm.

The importance of comparative anatomy

The evolutionary process is parsimonious. Although there are numerous exceptions, in general, evolution tends more to change existing structures than to produce new ones . Therefore, it is not strange that in different groups of animals the same structure has different functions.

For example, the bones in a bat’s wing, a whale’s fin, and a human arm are the same; this is called homology . On the other hand, it also frequently happens that different structures end up fulfilling the same function, in different organisms; in this case, we speak of analogies .

Comparative anatomy is the discipline that studies the similarities and differences of anatomical features based on their evolutionary proximity , and therefore analyzes these homologies and analogies. Thanks to comparative anatomy, it was possible to know that Therizinosaurus and Segnosaurus must have been closely related, and provided a new lens through which to observe the scythe lizard.

rebuilding the puzzle

Since evolution is a slow process, it is very common for closely related organisms to have similar anatomies. Comparative anatomy studies, not only with Segnosaurus , but also with the more recent remains of Enigmosaurus and Suzhousaurus , allow us to infer what Therizinosaurus looked like.

In fact, the discovery of dinosaurs belonging to the same group, but more primitive, such as Beipiaosaurus or Alxasaurus , made it possible to discover what characteristics were typical of the therizinosaurid family.

Today we know that it was a bipedal theropod, from the maniraptoran group —the same group to which birds, or Velociraptor— belong, which lived at the end of the Cretaceous, between 70 and 66 million years ago, in the territory that today is Asia. It was more than 9 meters long, had a small head, a beak in its mouth, a long neck, and a voluminous belly that it probably used to ferment food. Although we lack cranial material to tell us for sure, their close relatives were herbivorous animals, an unusual trait, since there are very few herbivores among theropods.

It probably used its huge claws to bring food closer to its mouth, although defense and sexual appeal are also possible functions attributed to these peculiar structures.

An even more peculiar feature is that, as it appears in the Jurassic World: Dominion trailer, both Therizinosaurus and the rest of the species of its family were fully or partially feathered dinosaurs . Its evolutionary proximity to many other feathered animals, such as birds, is a fairly reliable indication, but the strongest evidence is found, again, in a much closer relative, Beipiaosaurus , which we know had feathers.

A key piece of your ecosystem

One aspect of herbivorous dinosaurs that is often overlooked is their potential as seed dispersers.

Among modern birds, there is a direct relationship between seed dispersal and variables such as size, ability to retain seeds in their body, and speed of movement; hence the importance of animals such as the cassowary in their ecosystem: they transport many seeds and long distances.

Most of the herbivorous dinosaurs are either extraordinarily slow —such as the great long-necked sauropods, or the Triceratops— , or when they are fast, they are very small and retain seeds for a short time. But in the Therizinosaurus we find a middle ground; an animal weighing more than five tons, capable of consuming large amounts of fruit and transporting them over long distances .

A recent study estimates that these giants could retain the seeds in their digestive system between 4 and 18 days. If these estimates are true, it would imply that this giant with scythes in his hands would be a very important piece in the maintenance and renewal of the ecosystem to which he belonged.


A. Maleev. 1954. New tortoiseshell lizard in Mongolia. Nature, 3, 106−108.

Perry, G. L. W. 2021. How far might plant-eating dinosaurs have moved seeds? Biology Letters, 17(1), 20200689. DOI: 10.1098/rsbl.2020.0689

Xu, X. et al. 2009. A new feather type in a nonavian theropod and the early evolution of feathers. Proceedings of the National Academy of Sciences, 106(3), 832-834. DOI: 10.1073/pnas.0810055106

Zanno, L. E. 2010. A taxonomic and phylogenetic re-evaluation of Therizinosauria (Dinosauria: Maniraptora). Journal of Systematic Palaeontology, 8(4), 503-543. DOI: 10.1080/14772019.2010.488045

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