in walking resembled those of basal sauropodomorph dinosaurs. Their unique hip bones, which pointed backwards and were partially fused together, initially reminded paleontologists of the "bird-hipped" ornithischians. Among the most striking characteristics of therizinosaurs are the enormous claws on their hands, which reached lengths of around one meter in Therizinosaurus. The unusual range of motion in therizinosaur forelimbs, which allowed them to reach forward to a degree other theropods could not achieve, also supports the idea that they were mainly herbivorous. Therizinosaurs may have used their long reach and strongly curved claws to grasp and shear leafy branches, in a manner similar to large mammals that lived later on, such as chalicotheres, ground sloths, great apes, and giant pandas. Skin impressions from Beipiaosaurus indicate that therizinosaurs were covered with a coat of primitive, down-like feathers similar to those seen in the compsognathid Sinosauropteryx, as well as longer, simpler, quill-like feathers that may have been used in display. Classification and systematics Taxonomy Barsbold and Perle named the group Segnosauria as an infraorder of Theropoda in 1980. Dong Zhiming went further, placing the segnosaurs in their own order, Segnosaurischia. This name has been abandoned since the discovery that segnosaurs are a specialized group within the suborder Theropoda. Clark et al. 2004 considered Segnosaurischia a synonym of Therizinosauroidea. The clade Therizinosauria was first coined by Dale Russell in 1997—effectively replacing the older name Segnosauria, which has not yet been defined as a clade—to contain all therizinosaurian dinosaurs. The superfamily Therizinosauroidea was first coined in 1993 as a superfamily with no phylogenetic definition. The family Therizinosauridae had been established by Maleev in 1954 to include only the bizarre, giant-clawed theropod Therizinosaurus. Subsequent analyses have proven this family to be more diverse and synonymous with Segnosauridae. The following taxonomy follows Zanno 2010, unless otherwise noted. Branch Therizinosauria Genus Falcarius Genus Martharaptor Genus Jianchangosaurus Superfamily Therizinosauroidea Genus Beipiaosaurus Genus Enigmosaurus Genus Erliansaurus (more related to Therizinosauridae) Genus Neimongosaurus (more related to Therizinosauridae) Genus Suzhousaurus Family Alxasauridae (dubious utility) Family Therizinosauridae Phylogeny Therizinosauria is defined 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. When it was later realized that Therizinosaurus was an advanced therizinosaur more related to Alxasaurus than other dinosaur lineages, Therizinosauroidea was