In 1948, Soviet paleontologists found meter-long claws in the Gobi Desert and assumed they belonged to a giant turtle. Decades later, those claws turned out to be the hands of Therizinosaurus, a theropod dinosaur closely related to Velociraptor that had somehow evolved into a giant herbivore with the hips of a plant-eater, the claws of a ground sloth, the neck of a sauropod, and a beak. It looked like someone had assembled a dinosaur from spare parts.
Yuya Tamai from Gifu, Japan, CC BY 2.0, via Wikimedia Commons
The Turtle That Wasn't
In 1948, a joint Soviet-Mongolian expedition pushing into the Nemegt Formation of the Gobi Desert found something baffling. They uncovered three gigantic claws, each one nearly a meter long. The paleontologist in charge, Evgeny Maleev, studied the enormous, flattened blades. Based on their shape and what he thought were associated flat ribs, he concluded they belonged to a massive, turtle-like aquatic reptile that used the claws to harvest seaweed. In 1954, he named the creature Therizinosaurus cheloniformis, which means "turtle-formed scythe lizard".
For decades, this was all the world knew of Therizinosaurus. The creature remained a mystery, classified in its own unique family, Therizinosauridae, because it resembled nothing else in the fossil record. It wasn't until 1970 that Russian paleontologist Anatoly Rozhdestvensky suggested Maleev had it wrong, proposing the "scythe lizard" was actually a theropod dinosaur. But with only a few arm and claw bones to go on, the nature of the animal remained obscure.
Assembling a Frankenstein Dinosaur
The puzzle of Therizinosaurus started to come together with discoveries of its smaller, more complete relatives in the 1990s, such as Alxasaurus and Beipiaosaurus. These fossils allowed paleontologists to finally piece together a picture of one of the strange dinosaurs ever to exist. Therizinosaurus was indeed a theropod, a member of the same group that includes Tyrannosaurus and Velociraptor. Yet, it had abandoned its carnivorous ancestry for a completely herbivorous lifestyle.
This evolutionary shift resulted in a bizarre collection of anatomical features. Standing up to 5 meters tall and weighing over 5,000 kilograms, it was one of the largest known maniraptorans, the advanced theropod group that includes birds. It had a small skull on a long, slender neck, much like a sauropod. Its massive torso was wide and deep to accommodate a large gut for digesting plants, supported by a broad, backward-facing pelvis more typical of plant-eating dinosaurs than other theropods. It walked on four-toed feet, unlike the three-toed arrangement of its meat-eating cousins. The arms, each one was 2.5 meters long, ending in three fingers with the claws, the longest of any known land animal. Scientists now believe the claws were not for fighting, but for pulling down high branches to feed on leaves, a function similar to giant ground sloths.
💡Fun Facts
The name *Therizinosaurus* literally means "scythe lizard."
Evidence from close relatives like *Beipiaosaurus* suggests that *Therizinosaurus* was likely covered in primitive feathers.
The Nemegt Formation where it was found was not a sandy desert 70 million years ago, but a wet, forested river delta environment.
Despite its fearsome appearance, *Therizinosaurus* was a plant-eater that likely used its claws for defense or to intimidate predators like the tyrannosaur *Tarbosaurus*.
The Gobi Desert is an open, natural landscape with no official hours. Access is unrestricted but requires an experienced guide.
Admission
Free. However, reaching the remote location requires a significant budget for guided 4x4 tours.
Accessibility
The terrain is extremely rugged and undeveloped. Reaching the fossil beds requires multi-day travel in a 4x4 vehicle through remote desert with no paved roads or facilities.
The Therizinosaurus MysteryÖmnögovi Province, Mongolia
