A therizinosauroid dinosaur with integumentary structures from China
Therizinosauroidea ('segnosaurs') are little-known group of Asian dinosaurs with an unusual combination of features that, until recently, obscured their evolutionary relationships. Suggested affinities include Ornithischia(1), Sauroyodomorpha(2,3), Theropoda(4-11) and Saurischia sedis mutabilis(12). Here,ve describe a new therizinosauroid from the Yixian Formation (Early Cretaceous, Liaoning, China)(13). This new taxon provides fresh evidence that therizinosauroids are nested within the coelurosaurian theropods(8-11). Our analysis suggests that several specialized therizinosauroid characters, such as the Sauropodomorpha-like tetradactyl pes(1,2), evolved independently, within this group. Most interestingly, this new dinosaur has integumentary filaments as in Sinosauropteryx(14,15). This indicates that such feather-like structures may have a broad distribution among non-avian theropods, and supports the hypothesis that the filamentous integumentary structures may be homologous to the feathers of birds(14,15).