The relation between the more derived therizinosaurids and other theropods was greatly elucidated by the discovery of primitive members of the group, such as Beipiaosaurus in 1999 and Falcarius in 2005.
Srodnost između razvijenijih terizinosaurida i ostalih teropoda je velikim dijelom razjašnjena otkrićem primitivnih pripadnike ove grupe, kao što su Beipiaosaurus (1999.) i Falcarius (2005.).