a new species of Nothronychus (N. graffami) was named in 2009. With this, both species make Nothronychus the most complete therizinosaurid known. Description Therizinosaurids were quite advanced and robustly-built animals that reached multi-ton dimensions which make them among the largest maniraptorans. The smallest known therizinosaurids are Erliansaurus, Erlikosaurus and Neimongosaurus which were around long, furthermore the holotype skull of Erlikosaurus is about . Segnosaurus and the possible therizinosaurid Suzhousaurus were about the same size, in length and weighing . Slightly smaller members are represented by Nanshiungosaurus and Nothronychus, estimated at long and in weight, respectively. The related "Nanshiungosaurus" bohlini was similar in size (about long), however, its assignment to Nanshiungosaurus is unlikely and it may or not represent another species or specimen of the better known Suzhousaurus. Therizinosaurus were the largest representatives, reaching the top dimensions of the group, they grew up to long weighing over . These dimensions that make the genus among the largest-known theropods. The exponential sizes obtained across the Therizinosauridae appear to have been triggered by the bulk and specialized diet within the group and early members of the Therizinosauria. Skin impressions from Beipiaosaurus and Jianchangosaurus indicate that primitive therizinosaurs were covered with a coat of down-like, sparse feathers similar to those seen in the compsognathid Sinosauropteryx, as well as longer, simpler, quill-like feathers that may have been used in display. However, while the earliest known example of primitive, stage-I feathers are found among early therizinosaurs, more advanced members are thought to have possessed more developed, avian-like feathers. Although typically associated with flight, the feathers which covered these animals were not used for that purpose, instead, they assisted in either metabolism or display. Skull Therizinosaurids had more specialized skulls compared to primitive members such as Falcarius, which had a generalist, beak-less snout. They had relatively elongated snouts and the tip was covered with a rhamphotheca (keratinous beak) used during feeding. Although the extension of the beak on the dorsal surface of the snout is unknown, it is estimated that it slightly overlapped the nasal cavity as in some modern-day birds. The dentary (lower jaw) also developed a rhamphotheca, seen on the edentulous (without teeth) anterior-most end. This extension was supplied by neurovascular foramina (small pits) found on the lateral surfaces. The known specimens of the therizinosaurids Erlikosaurus, Neimongosaurus and Segnosaurus preserve numerous neurovascular foramina (more notorious on Erlikosaurus), indicating that a well-developed beak was present in