In August 1999, in the Eren Basin of Inner Mongolia, a new genus of Therizinosaurus is discovered, named by experts as Neimenggusaurus. Fossils of skull, cervical vertebra, sacral vertebra, caudal vertebra, pubic bones, ischium, hipbones, paws and teeth were excavated on the spot.

The newly unearthed Neimenggusaurus is a kind of medium-to-small-sized omnivorous dinosaur living in 80 million years ago. Being two meters long and less than one meter high, with a long and narrow head, a super longneck, hooked paws, sharp teeth and a long and thin tail, it is not completely the same as the previously discovered Therizinosaurus. With no less than 14 cervical vertebras, it is a Therizinosaurus with the longest neck ever known.

According to the fossils of Neimenggusaurus, experts inferred that its actual neck is about 0.7 meter long. But the previously unearthed Therizinosaurus all possess a feature of being short-necked. The excavation of Inner Mongolia dinosaur supplied new materials for dinosaur taxonomy and enriched the dinosaur family of the Cretaceous Period as well.