Therizinosaurs

By | September 9, 2016

When scientists put together bits and pieces of therizinosaur fossils, they turned out to be some of the most bizarre-looking dinosaurs ever. They were tall with small heads, stumpy feet, and pot bellies. While their bones show they were relatives of predatory dinosaurs, their teeth and digestive system seem to have evolved to eat plants instead of meat.

FAMILY FACT FILE

Key features
■ Long necks
■ Enormous curved claws on fingers
■ Short tails
■ Four-toed feet
■ Partly feathered

When
Therizinosaurs first appeared in the Early Cretaceous, 130 million years ago. They died out in the Late Cretaceous, 65 million years ago.

therizinosaur-baby-egg

Model based on a fossilized therizinosaur embryo found inside an egg.

Therizinosaurus (THERRY-zin-oh-SORE-us)

therizinosaurs


When: 80–70 million years ago (Late Cretaceous)

Fossil location: Mongolia

Habitat: Woodlands

Length: 26–36 ft (8–11 m)

Diet: Plants

Therizinosaurus was one of the bigger therizinosaurs. Its fossils were found in what is now the cold, barren Gobi Desert. During the Late Cretaceous, this region was warmer and wetter, with tall trees. Perhaps Therizinosaurus’s immense height helped it to gather leaves from tall trees, like a giraffe.

SCISSOR HANDS

fossil-of-therizinosaurus-claw

A fossil of a Therizinosaurus’s claw

Therizinosaurus had astonishingly long claws on its hands, each measuring nearly 3 ft (1 m) long. These may have been defensive weapons used for slashing at tyrannosaurids, such as the Tarbosaurus shown here. They might also have been used to pull high branches down from trees.

Alxasaurus (ALK-sah-SORE-us)

alxasaurus


When: 130 million years ago (Early Cretaceous)

Fossil location: China

Habitat: Woodlands

Length: 13 ft (4 m)

Diet: Plants

In 1988, five specimens of a previously unknown dinosaur were found in Mongolia. This was Alxasaurus, a therizinosaur. Its leaf-shaped teeth were not sharp enough to tear off flesh, so it probably fed on plants. The swollen stomach of Alxasaurus indicates that it ate great quantities of leaves. Its big belly may have made it too clumsy to run fast. If attacked by another dinosaur, it probably lashed out with its claws rather than trying to escape.

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