Therizinosaurus

Therizinosaurus meaning 'scythe lizard' was a very large genus of therizinosaurid dinosaurs that lived during the Late Cretaceous period in what is now Asia.

The first remains of Therizinosaurus were found in 1948 by a Mongolian field expedition in the Gobi Desert and later described by Evgeny Maleev in 1954. This dinosaur stood out because of its very long, stiffened claws on its forelimbs.

Therizinosaurus could grow up to 9–10 m (30–33 ft) long and 4–5 m (13–16 ft) tall. It had a long neck and a wide body, which would have helped it eat leaves high up in trees. Its forelimbs were very strong and had three fingers with extremely long claws. These claws were likely used for pulling vegetation within reach rather than for attack or defense because they were too fragile for fighting.

Therizinosaurus was one of the last and largest members of its unique group, the Therizinosauria. For many years, scientists were unsure where it fit among dinosaurs, but it is now placed among the Theropoda, specifically as maniraptorans. Its unusual body shape shows how different species can evolve similar traits to adapt to their environment, much like some herbivorous mammals. Despite its imposing claws, Therizinosaurus was probably a peaceful browser, using its arms to reach high foliage and stay safe from predators like tyrannosaurid Tarbosaurus.

History of discovery

In 1948, scientists from the USSR Academy of Sciences looked for fossils in the Nemegt Formation in the Gobi Desert of Southwestern Mongolia. They found many dinosaur and turtle fossils. Among these, they found three large claw bones from a dinosaur's hands.

In 1954, a scientist named Evgeny Maleev described these claws. He named the dinosaur Therizinosaurus cheloniformis. The name means “scythe lizard” because of its large hand claws. The part “cheloniformis” refers to its turtle-like look.

Later, more fossils were found. These included parts of the arms and legs. The new fossils helped scientists learn that Therizinosaurus was a type of theropod dinosaur, not a turtle. They showed it had long, strong arms with huge claws. This confirmed it was part of a group of dinosaurs called therizinosaurs.

Description

Therizinosaurus was a very large dinosaur, measuring 9 to 10 meters (30 to 33 feet) long. It weighed between 5 to 10 tons, about as much as an elephant. It had a small head with a beak-like shape on top of a long neck, and it walked on two legs. It likely had feathers, though not many.

The most notable feature of Therizinosaurus were its huge claws on each hand, the longest known from any land animal. Its arms were very long, and its body was made for eating plants, showing it was a herbivore. Its legs were strong, and its feet had four toes that helped it walk, unlike most other similar dinosaurs which usually had three.

Classification

See also: Timeline of therizinosaur research

Evgeny Maleev first thought Therizinosaurus was a giant sea turtle. Later, scientists learned it was a type of theropod dinosaur. In 1970, Anatoly Rozhdestvensky said that what looked like ribs in the fossil might have come from another dinosaur. By the 1990s, discoveries like Alxasaurus helped scientists learn that Therizinosaurus was an unusual theropod, related to birds. These dinosaurs had long, strong claws and feathers.

Paleobiology

Scientists have studied how Therizinosaurus might have lived and eaten. They noticed that Therizinosaurus and some old mammals had strong arms and legs. These features probably helped them both. Because animals with such bodies often eat plants, scientists think Therizinosaurus ate leaves from trees and shrubs. Its long neck would have helped it reach high branches, and its long arms could have grabbed food.

Recent studies have looked at Therizinosaurus's famous long claws. When it was first found in 1954, some scientists thought the claws were for grabbing seaweed. Others thought they could open insect nests, dig in soil, or defend against predators. New computer tests show the claws were probably not strong enough for heavy digging but good for pulling or grabbing plants. Some scientists think the claws were mostly for show and grew bigger as the dinosaur got older.

Paleoenvironment

The remains of Therizinosaurus were found in the Nemegt Formation in the Gobi Desert. This area had rivers and forests and many kinds of dinosaurs lived there, including Therizinosaurus.

Other dinosaurs that lived in the same area included Deinocheirus, Saurolophus, Nemegtosaurus, and the large predator Tarbosaurus. Therizinosaurus was very tall, so it could reach food that other dinosaurs could not. Its long claws might have helped it defend itself against predators.