Therizinosaurus

*Therizinosaurus cheloniformis*

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***Therizinosaurus***, meaning 'scythe lizard' from the Greek "therizo" meaning 'to reap' or 'to cut off' and "sauros" meaning 'lizard') was a very large therizinosaurid (previously known as segnosaur). It could grow up to 10 meters (33 feet) long and reach nearly 6 tonnes in weight. *Therizinosaurus* lived in the late Cretaceous (late Campanian-early Maastrichtian stages, around 70 million years ago), and was one of the last and largest representatives of its unique group, the Therizinosauria ('reaping lizards'). It is known only from a few bones, including gigantic hand claws, from which it gets its name. Also, studies have shown that the Therizinosaurs were actually maniraptorans rather than a strange genus of sauropod like previously thought, due to the hip alignment of the creature.

## Anatomy

*Therizinosaurus* had a small head with a beaked mouth, atop a long neck. It was bipedal and had a large, heavy, deep body, as evidenced by the wide pelvis, 2.5 meter (8 foot) long arms and legs that ended in four toes (three of which supported the animal's weight), which were tipped by short, curved claws. The most distinctive feature of the animal was the presence of three gigantic claws on its front limbs. Each of the three digits of its hand bore these claws, which reached nearly a meter (approximately 3.3 feet) in length. The largest claw was on the first digit. The feeding habits of *Therizinosaurus* are still debated, but it was most probably an herbivore, using its big claws to push leaves into its mouth. Other hypotheses suggest that it was a termite eater, using its claws to open large termite nests - but it seems highly unlikely that an animal the size of *Therizinosaurus* could survive on a diet based on insects and features of the skull (including a beaked mouth and flattened teeth) suggest a herbivorous diet. Based off of much research and data collected, it is found that this species had a strange addiction to plants.
There are other possible functions that could have been served by the claws of *Therizinosaurus*, such as defense against predators (e.g. the contemporary *Tarbosaurus*) and in intraspecific fighting, such as fighting for territory or for mating. Although studies show that therizinosaur claws were bad at piercing and digging, so they may have been used for intimidation, eating and display instead. Despite this, their arms were very powerful.
Based on *Beipiaosaurus*, T*herizinosaurus* may have had two layers of feathers, one a shorter, almost downy layer, and the second one a longer, quill like layer. The feathers around the neck had the ability to be puff out, probably as a display structure. It did not have pennaceous feathers.

*Therizinosaurus* is ancient greek for "Reaping Lizard", referring to the large, curved claws of the forelimb .The only and type species is *T. cheloniformis*, meaning Turtle Shaped Reaping Lizard, referring to the fact that the claws were originally thought to belong to an extinct giant turtle.

## Discovery and Species

The first fossils now attributed to *Therizinosaurus* were discovered in the late 1940s by a joint Soviet-Mongolian fossil expedition. The expedition unearthed several giant claws that measured up to a meter in length. However, it was not known what creature these belonged to until the early 1950s, when further fossil expeditions unearthed more bones: several more sets of claws and parts of
a forelimb and hindlimb. Subsequent finds in northern China allowed paleontologists to assemble the general skeletal structure of the animal, which was determined to be a dinosaur and not a turtle.

The recent discovery of several related dinosaurs - *Alxasaurus* in 1994 and *Beipiaosaurus* in 1999 - helped clarify the position of the therizinosaurs as a whole. Various theories had been proposed to explain the ancestry of these dinosaurs, with some scientists even suggesting they were descendents of (info needed) - but these new, well-preserved finds, giving details about the bird-like pelvis, feet and skulls, helped confirm that the therizinosaurs were all maniraptoran theropod dinosaurs.

## Trivia

* When the first fossils of the *Therizinosaurus* were found, they were misidentified as the skeleton of a large turtle.
* The only known specimens of the animal are of the arms and legs.

## JPInstitute.com Description

This strange looking dinosaur had claws that were 3 feet (1 m) long! It is also the longest of its family, the therizinosaurs, yet discovered. It is now thought that it may have had feathers, as others in its family have been found to show the remains of protofeathers in their fossils.

Known from only partial remains, the claws and huge arms of this dinosaur are astounding. Therizinosaurus has been an intriguing puzzle for scientists ever since several huge claws were first discovered in 1948. In the late 1950s, a number of different bones were found, including a tooth, another large claw and parts of the front and rear limbs that also included a four-toed foot. These bones were so bizarre that paleontologists didn't know what to make of them except to classify them together because of the strange claws.

A series of finds in Mongolia in the late 1980?s showed that huge arms that had been previously attributed to Deinocheirus, actually belonged to the same group as the huge claws and strange bones attributed to Therizinosaurus. Parts of the pelvis and other bones were also found, which gave paleontologists a better look at what was shaping up to be the strangest dinosaur ever to walk the earth.

While the claws were very long, they were not sharply curved. In cross section, they were quite thin. Some scientists think they were used to tear open termite mounds. Therizinosaurs had a fairly long neck, small head, and teeth that could have been used to eat plants. The family previously known as segnosaurs is now named after this peculiar dinosaur.

## Dinosaur Field Guide Description

Therizinosaurus ("scythe lizard") is enormous. It is also one of the most bizarre dinosaurs. Although it is a theropod (or meat-eating) dinosaur, it most likely ate just plants! It had gigantic claws, the largest over 28 inches (70 cm) long, but these claws were not curved and hooked like the claws of a predator. Instead, they were flat and straight. Therizinosaurus was a giant relative of Beipiaosaurus. That earlier dinosaur was covered by protofeathers, a simple body covering that in some other dinosaurs (including oviraptorosaurs and birds) became true feathers. Because the earlier therizinosaur Beipiaosaurus had these protofeathers, paleontologists suspect that Therizinosaurus had them, too. Therizinosaurus's upper arm bone is almost 3 feet (1 m) long. It may have been used to break branches off of trees. It may seem strange to think of a plant-eater as a member of a group of meat-eating animals, but this is not the only case of that happening. For example, the modern giant panda eats almost nothing except bamboo, but it is a member of the carnivorous mammal group.

### Fun Facts

Therizinosaurus has the largest finger bones of any known animal in Earth's history.

### Trivia

When paleontologists first found Therizinosaurus, they thought it was some kind of giant turtle!

## Links

https://web.archive.org/web/20040806045354fw\_/http://www.jpinstitute.com/dinopedia/dinocards/dc\_theri.html
https://web.archive.org/web/20080706033143/http://kids.yahoo.com/dinosaurs/123--Therizinosaurus

## References

* https://museum.wa.gov.au/explore/dinosaur-discovery/therizinosaurus
* https://www.nhm.ac.uk/discover/dino-directory/therizinosaurus.html
* https://www.dkfindout.com/us/dinosaurs-and-prehistoric-life/dinosaurs/therizinosaurus/
* https://www.britannica.com/animal/therizinosaur
* https://nature.ca/notebooks/english/therizi.htm
* https://dinosaurpictures.org/Therizinosaurus-pictures
* https://aapt.scitation.org/doi/abs/10.1119/1.5055323