The clade Therizinosauria was first defined by Dale Russell in 1997 as Alxasaurus, Enigmosaurus, Erlikosaurus, Nanshiungosaurus, Segnosaurus, Therizinosaurus, and all taxa closer to them than to oviraptorosaurs, ornithomimids, and troodontids.
Paul Sereno, in 2005, modified this definition to the most inclusive clade containing Therizinosaurus but not Ornithomimus, Oviraptor, Shuvuuia, Tyrannosaurus, or Troodon.

Therizinosauroidea, previously named as a superfamily with no phylogenetic definition, was first defined by Zhang et al.
in 2001, as the clade containing all theropods more closely related to Therizinosaurus than to birds (effectively replacing the older name Segnosauria, which has not yet been defined as a clade).
This definition, however, defines the same group as the pre-existing Therizinosauria.
An alternate definition was given by Clark in 2004 (as the last common ancestor of Therizinosaurus and Beipiaosaurus and all its descendants), comprising a narrower group that excludes more primitive therizinosaurs, such as Falcarius, and allows the name Therizinosauria to remain in use for the larger group comprising all therizinosaurs.
This definition was followed by Teresa Maryańska and Barsbold (2004), Sereno (2005), Zanno et al. (
2009) and Zanno (2010), though other subsequent studies, such as Senter (2007, 2012) have continued to use Therizinosauroidea for the therizinosaur "total group".

The cladogram below follows the extensive phylogenetic analysis of the Therizinosauria by Lindsay E. Zanno in 2010.

The following cladogram is based on the phylogenetic analysis by Phil Senter et al.
2012.

The cladogram below is the cladogram based on the phylogenetic analysis of Therizinosauria conducted by Hanyong Pu et al.
2013.

Below is the recently performed phylogenetic analysis performed by Hartman et al.
2019 using the data provided by Zanno in 2010:
The clade Therizinosauria was first defined by Dale Russell in 1997 as Alxasaurus, Enigmosaurus, Erlikosaurus, Nanshiungosaurus, Segnosaurus, Therizinosaurus, and all taxa closer to them than to oviraptorosaurs, ornithomimids, and troodontids. Paul Sereno, in 2005, modified this definition to the most inclusive clade containing Therizinosaurus but not Ornithomimus, Oviraptor, Shuvuuia, Tyrannosaurus, or Troodon.
Therizinosauroidea, previously named as a superfamily with no phylogenetic definition, was first defined by Zhang et al. in 2001, as the clade containing all theropods more closely related to Therizinosaurus than to birds (effectively replacing the older name Segnosauria, which has not yet been defined as a clade). This definition, however, defines the same group as the pre-existing Therizinosauria. An alternate definition was given by Clark in 2004 (as the last common ancestor of Therizinosaurus and Beipiaosaurus and all its descendants), comprising a narrower group that excludes more primitive therizinosaurs, such as Falcarius, and allows the name Therizinosauria to remain in use for the larger group comprising all therizinosaurs. This definition was followed by Teresa Maryańska and Barsbold (2004), Sereno (2005), Zanno et al. (2009) and Zanno (2010), though other subsequent studies, such as Senter (2007, 2012) have continued to use Therizinosauroidea for the therizinosaur "total group".
The cladogram below follows the extensive phylogenetic analysis of the Therizinosauria by Lindsay E. Zanno in 2010.
The following cladogram is based on the phylogenetic analysis by Phil Senter et al. 2012.
The cladogram below is the cladogram based on the phylogenetic analysis of Therizinosauria conducted by Hanyong Pu et al. 2013.
Below is the recently performed phylogenetic analysis performed by Hartman et al. 2019 using the data provided by Zanno in 2010:
Therizinosauria