It was one of the last and the largest representative of its unique group, the Therizinosauria. "Therizinosaurus" is classified as a therizinosaurid, meaning it was more derived (advanced) than the primitive therizinosauroids. At first, therizinosaurs had very complex relationships due to the lack of genera and findings at the time. Originally, they were thought to be some kind of Cretaceous sauropodomorphs or transitional ornithischians, but after years of taxonomic debate they are now placed within the Theropoda, specifically as maniraptorans. The unusually elongated hand claws of "Therizinosaurus" were more useful when pulling vegetation within reach rather than being used for attack or defense. "Therizinosaurus" was a very tall animal, likely having a reduced competition over the foliage and outmatching predators like "Tarbosaurus".