Question 1

How do you say Therizinosaurus?

Accepted Answer

You say it like this: theh-RIZ-in-oh-SORE-us. Break it into five chunks and say each one out loud: theh, then RIZ, then in, then oh, then SORE-us. The stress falls on the second syllable, RIZ, and then again on SORE. Once you say it a couple of times, it starts to feel pretty natural, and it is definitely one of the most impressive dinosaur names you can drop in a conversation.

Question 2

What does Therizinosaurus mean?

Accepted Answer

Therizinosaurus means scythe lizard in Ancient Greek. The first part of the name, therizino, comes from the Greek word therizein, which means to reap or cut with a scythe, that big curved blade farmers used to harvest crops. Scientists chose this name because Therizinosaurus had enormous curved claws that looked just like giant scythe blades. The second part, saurus, simply means lizard, as it does in almost every dinosaur name.

Question 3

How big were Therizinosaurus claws?

Accepted Answer

The claws of Therizinosaurus were absolutely record-breaking, reaching close to one meter, or about three feet, in length. That makes them the longest claws of any known animal in the entire history of life on Earth, a record that still stands today. To picture it, each claw was roughly as long as the arm of an average adult human from shoulder to fingertip. They were thick and strongly curved, more like giant sickle blades than the slender claws you might picture on a cat or eagle.

Question 4

Was Therizinosaurus a carnivore or herbivore?

Accepted Answer

Therizinosaurus was almost certainly a herbivore, a plant-eater, which surprises most people given its terrifying appearance. Despite being related to meat-eating theropods like T. rex and Velociraptor, Therizinosaurus evolved in a completely different direction. Its wide barrel belly was built to digest massive amounts of plant material, and its jaws show adaptations for cropping vegetation rather than tearing flesh. Scientists are very confident about this because its smaller, better-preserved relatives all show the same herbivorous features.

Question 5

When did Therizinosaurus live?

Accepted Answer

Therizinosaurus lived during the Late Cretaceous period, roughly 72 to 66 million years ago. It was alive right up near the end of the age of dinosaurs, dying out in the mass extinction event 66 million years ago that wiped out all non-bird dinosaurs. Its fossils come from the Nemegt Formation in Mongolia, which was laid down during exactly this time period by ancient river systems flowing across what is now the Gobi Desert.

Question 6

How big was Therizinosaurus?

Accepted Answer

Therizinosaurus was a genuinely massive animal. Scientists estimate it reached about 33 feet, or 10 meters, in length, which is roughly the length of two minivans parked bumper to bumper. Its weight is estimated at around 5,000 kilograms, or about 11,000 pounds, making it heavier than a full-grown African elephant. It walked on two legs, but its upright posture and long neck meant it could reach vegetation up to about 5 meters, or 16 feet, off the ground.

Question 7

Where was Therizinosaurus found?

Accepted Answer

Therizinosaurus fossils were found in the Nemegt Formation in the Gobi Desert of Mongolia. The first remains were discovered in 1948 during a Mongolian field expedition, and additional bones were collected through the 1960s, 1970s, and 1980s. The Nemegt Formation is one of the richest dinosaur fossil sites in the world, and it has also produced the bones of other famous dinosaurs like Tarbosaurus and Saurolophus.

Question 8

Did Therizinosaurus have feathers?

Accepted Answer

Scientists strongly believe Therizinosaurus was feathered, although no feather impressions have been found directly on Therizinosaurus fossils themselves because the known remains are so fragmentary. The evidence comes from its close relative Beipiaosaurus, discovered in China in 1999 with beautifully preserved feather impressions, which confirmed that therizinosaurids were feathered animals. Given how closely related these dinosaurs are, it would be very surprising if Therizinosaurus was not also covered in at least some form of feathers or feather-like filaments.

Question 9

Why did Therizinosaurus have such huge claws if it only ate plants?

Accepted Answer

Scientists think the enormous claws served at least two purposes. The main job was feeding: Therizinosaurus likely used those massive hooked claws to grab onto high branches and pull them down to its mouth, giving it access to leaves that other animals simply could not reach. As a bonus, those same claws would have been a spectacular defense against predators. Even a hungry Tarbosaurus, the apex predator of its ecosystem, would have had to think very carefully before attacking an adult Therizinosaurus armed with meter-long hooks on each hand.

Question 10

Is Therizinosaurus related to T. rex?

Accepted Answer

Yes, distantly. Both Therizinosaurus and T. rex are theropod dinosaurs, meaning they share a common ancestor and belong to the same broad group. However, they evolved in very different directions over millions of years. T. rex became one of history's greatest predators, while Therizinosaurus evolved into a giant plant-eater with enormous claws. They are a little like how humans and monkeys are both primates but look and behave very differently. In the Cretaceous ecosystem, the Therizinosaurus equivalent of T. rex was Tarbosaurus, which actually shared its Mongolian habitat.

Question 11

Who discovered Therizinosaurus?

Accepted Answer

The first fossils were found in 1948 during a Mongolian field expedition in the Gobi Desert, but the dinosaur was formally named and described by Soviet paleontologist Evgeny Maleev in 1954. Maleev is the scientist who recognized the remains as belonging to a large dinosaur rather than a turtle, which had been the initial guess when those enormous claw-like structures were first uncovered. More bones were found by subsequent expeditions from the 1960s through the 1980s, gradually building up the limited but fascinating picture we have today.

Question 12

How do we know what Therizinosaurus looked like if barely any bones were found?

Accepted Answer

This is one of paleontology's great challenges with Therizinosaurus, and scientists handle it by studying its close relatives. No skull of Therizinosaurus has ever been discovered, so researchers look at animals like Erlikosaurus, whose skull was found in the same Nemegt Formation, and Beipiaosaurus from China, which was preserved with feathers. By combining the actual Therizinosaurus bones we have, including its spectacular claws and limb elements, with detailed knowledge of its relatives, scientists can build a reliable reconstruction. It is a bit like completing a jigsaw puzzle using pieces from a very similar puzzle to fill the gaps.

Question 13

Could Therizinosaurus have used its claws to fight other dinosaurs?

Accepted Answer

Almost certainly yes, at least in self-defense. While Therizinosaurus evolved those enormous claws primarily for feeding, they would have been formidable weapons if the animal was threatened. A single swipe from a claw nearly one meter long could inflict devastating injuries on an attacker. Scientists think that for most predators in the Nemegt ecosystem, the combination of Therizinosaurus's huge size and its terrifying claws would have been enough of a deterrent to keep them from attacking healthy adults. Juveniles and sick individuals would have been much more vulnerable.

Question 14

What other dinosaurs lived at the same time and place as Therizinosaurus?

Accepted Answer

Therizinosaurus shared the Nemegt Formation ecosystem in what is now Mongolia with a fascinating cast of dinosaurs. The top predator in its world was Tarbosaurus, a close Asian relative of T. rex. Giant plant-eaters included the long-necked sauropod Opisthocoelicaudia and the massive hadrosaur Saurolophus, which also lived in North America. Smaller dinosaurs like the ostrich-mimic Gallimimus and the egg-thief Oviraptor also roamed this ancient landscape. It was a rich, diverse ecosystem that paleontologists are still actively studying today.

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