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Therizinosaurus

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Therizinosaurus was a colossal dinosaur that lived during the Late Cretaceous period.

Therizinosaurus Restoration
Therizinosaurus Restoration

It inhabited the regions of what is now Asia. This genus belongs to the Therizinosauria, a unique group of dinosaurs.

Therizinosaurus known material
Therizinosaurus known material

Scientists identify it as a massive maniraptoran. Maniraptorans are a major group of dinosaurs that includes birds. Therizinosaurus stands out as one of the largest known members of this clade. Its massive size allowed it to occupy a specific niche in its environment. It likely faced less competition for foliage because of its height. It could also outmatch large predators like the tyrannosaurid Tarbosaurus.

The anatomy of Therizinosaurus suggests it was a specialized herbivore.

Therizinosaurus arm diagram
Therizinosaurus arm diagram

It possessed a long neck to reach high vegetation. A rhamphotheca, which is a horny beak, helped it process plants. Its wide torso provided space for a large gut to digest foliage. The animal had a semi-erect, bipedal gait, meaning it walked on two legs. Its hindlimbs were unique among theropods. The feet ended in four functionally weight-bearing toes. This differs from other theropod groups where the first toe is a reduced dewclaw. This foot structure actually resembles the more distant sauropodomorphs.

The most striking feature of Therizinosaurus was its enormous manual unguals.

Therizinosaurus ungual morphology
Therizinosaurus ungual morphology

Unguals are the bony parts that form the claws. These claws were exceptionally long, reaching over 72 centimeters in length. Unlike its relatives, these claws were very stiff and elongated. They only showed significant curvature at the very tips.

Therizinosaurus claws lateral
Therizinosaurus claws lateral

Scientists believe these claws were not for active attack or defense. The claws were actually quite fragile. Instead, they were likely used to pull vegetation within reach. They may have also served a role in intimidation. The arms were robust and resistant to stress, suggesting heavy use.

The history of discovering Therizinosaurus is a story of scientific debate.

Therizinosaurus PIN 551-483 unguals
Therizinosaurus PIN 551-483 unguals

In 1948, a Mongolian field expedition found the first remains. These fossils were located in the Nemegt Formation of the Gobi Desert. The expedition was organized by the USSR Academy of Sciences. They found three partial manual unguals at a site called Quarry V. In 1954, the paleontologist Evgeny Maleev described these bones. He named the genus Therizinosaurus, which means "scythe lizard." He also named the species cheloniformis, meaning "turtle-shaped." This was because he thought the animal was a large, turtle-like reptile.

As more fossils were found, the classification of the animal changed.

Therizinosaurus MPC-D 100 15 arms
Therizinosaurus MPC-D 100 15 arms

In 1970, Anatoly K. Rozhdestvensky suggested it was actually a theropod. He compared the claws to the dinosaur Chilantaisaurus. Later, Rinchen Barsbold described more complete specimens in 1976. This included the MPC-D 100/15 specimen, which contained arms and ribs. These findings helped prove the animal was a theropod. In 1982, Altangerel Perle described a right hindlimb found at Hermiin Tsav. This specimen, MPC-D 100/45, helped clarify the foot structure. By 2010, Lindsay E. Zanno conducted a large taxonomic reevaluation. She confirmed the link between these various remains.

The scale of Therizinosaurus was truly immense.

therizinosaurus size
therizinosaurus size

Estimates of its size vary among different researchers. Gregory S. Paul estimated the weight at approximately 3 tons in 2024. However, Thomas R. Holtz Jr. suggested it could weigh as much as an elephant. In 2013, Lindsay E. Zanno and Peter J. Makovicky estimated a weight of around 5,000 kilograms. These numbers highlight its status as a giant among maniraptoriforms. It was one of the largest animals in its ecosystem. Its massive body and long claws made it a singular creature of the Cretaceous.

Therizinosaurus provides an important look at how animals adapt.

Therizinosaurus known material
Therizinosaurus known material

Its body shape is an example of convergent evolution. This occurs when different species evolve similar traits to solve similar problems. Therizinosaurus shared feeding habits with chalicotheriines, which are herbivorous mammals. This suggests that different types of animals can develop similar tools for eating plants. Studying Therizinosaurus helps scientists understand the diversity of the Theropoda clade. It shows how even meat-eating lineages can evolve into massive plant-eaters. This makes the study of this "scythe lizard" vital to paleontology.

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🖼️ Images & Media (28)
File:Cretaceous-aged dinosaur fossil localities of Mongolia.PNG
Cretaceous-aged dinosaur fossil...
File:Therizinosaurus PIN 551-483 unguals.jpg
Therizinosaurus PIN 551-483 unguals.jpg
File:Therizinosaurus MPC-D 100 15 arms.jpg
Therizinosaurus MPC-D 100 15 arms.jpg
File:Therizinosaurus known material.jpg
Therizinosaurus known material.jpg
File:therizinosaurus size.png
therizinosaurus size.png
File:Therizinosaurus Restoration.png
Therizinosaurus Restoration.png
File:Therizinosaurus arm diagram.png
Therizinosaurus arm diagram.png
File:Therizinosaurus ungual specimens.png
Therizinosaurus ungual specimens.png
File:Therizinosaurus ungual morphology.png
Therizinosaurus ungual morphology.png
File:Therizinosaurus IGM 100 45 diagram.png
Therizinosaurus IGM 100 45 diagram.png
File:Erlikosaurus.jpg
Erlikosaurus.jpg
File:Alxasaurus Tyrrell.jpg
Alxasaurus Tyrrell.jpg

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