Therizinosaurus was an unusual theropod—one that was probably not carnivorous, but herbivorous—from East Asia in the Late Cretaceous. It had a small head with a toothless beak. Its long neck, broad, heavy body and relatively short tail were all covered with feathers. Its close relatives, the therizinosaurs, all belonged to a group of bird-like dinosaurs called the maniraptors. Therizinosaurus’s feathers might have been both for body insulation and for display during mating. It had short, four-toed feet. Therizinosaurus's most distinctive feature was the presence of three gigantic finger-claws, gently curved, flat-sided and tapering. The longest of these was one metre (more than 3 feet) long.

Fossil studies

Therizinosaurus means “scythe lizard”, after its immensely long claws. Its skull has never been discovered. Reconstructions have been based on the skulls of related species. Therizinosaurus and its relatives, all of which looked like giant, flightless birds with outsize claws, were probably the most unusual dinosaurs ever discovered.

Possible uses for claws

Palaeontologists have speculated on the uses for Therizinosaurus's huge claws. They have several theories, apart from the obvious use in defence: the fearsome claws would have certainly deterred a giant predator such as Tarbosaurus from attacking it. They may have enabled Therizinosaurus to rip open termite nests and devour vast quantities of the insects clustered inside.

An alternative purpose might have been for raking out water plants or pulling down branches to eat leaves. But perhaps the likeliest explanation is that large claws may have played a part in male courtship display, or in fighting between rival males. The most impressive set of claws would have impressed females and intimidated rivals.

Facts about Therizinosaurus

Pronunciation: THER-ee-ZINE-oh-SAW-rus

Size: 10 m (33 ft) long and 5 m (16.5 ft) tall; weighed up to 6 tonnes

Where and when: Riverside woodland in East Asia, 70 million years ago (Late Cretaceous)

Diet: Although classified as a theropod, it probably ate only plants or possibly termites

Predators: Tarbosaurus

Features: Gigantic claws with multiple uses; long neck allows it to reach into high branches; massive size deters predators

Relatives: Segnosaurus, Nanshiungosaurus, Alxasaurus, Beipiaosaurus (all East Asia)