AGE:
Late Cretaceous (Late Campanian-Early Maastrichtian), Nemegt Formation, 70 million years ago

SIZE:
Therizinosaurus arm was about 2.5 metres long, scythe-like claw 70 cm long around its outer curve;

Deinocheirus arms about 2.6 metres long

MEANING OF NAME:
Therizinosaurus - 'Scythe reptile'

'Deinocheirus, 'Terrible hand'

PRONUNCIATION:
Ther-ih-sen-oh-SAWR-us

Dine-oh-KIR-us

CLASSIFICATION:
THEROPODA: relationships uncertain

For many years Therizinosaurus cheloniformis and Deinocheirus mirificus presented palaeontologists with a puzzle. Evidently somehow related to the theropods or carnivorous dinosaurs, the function of their large claws and their attendant forelimbs was a mystery. Certainly, they had to belong to animals quite unlike Tarbosaurus bataar with its highly reduced forelimbs and yet they were animals clearly in the same size category.

Material that has recently come to light in China suggests that these animals were as atypical of large carnivorous dinosaurs as pandas are atypical of bears. Like pandas, they were probably gentle herbivores. They used their large forelimbs and claws to pull down branches on which to browse.

The claws with the horny sheath that would have fitted over the outside of the bone may have been up to one metre long. Some palaeontologists have even suggested that therizinosaurs may have used the huge claws for ripping into ant nests.

Therizinosaurus cheloniformis and Deinocheirus mirificus were browsers in forests with the view that conditions in Central Asia has become much more moist than what they had been like 10 million years before these dinosaurs lived.