TYPE SPECIES:
• B. inexpectus Xu, Tang & Wang, 1999 "unexpected Beipiao lizard"

Animalia
Vertebrata
Tetrapoda
Sauropsida
Archosauromorpha
Ornithodira
Dinosauria
Theropoda
Tetanurae
Coelurosauria
Therizinosauria

The fourth non-avian discovered to have feathers or feather-like integument, from the same Early Cretaceous Chinese deposits as the other four (Sinosauropteryx, Protarchaeopteryx, Caudipteryx, and most recently Sinornithosaurus). Beipiaosaurus' integument seems somewhat similar to that of Sinosauropteryx, but longer -- 5 cm on the average and up to 7 cm on the arms. The ends seem to have branching structures.

Apart from the integument, Beipiaosaurus, a primitive therizinosaur, has features which show therizinosaurs to be coelurosaurian theropods, not sauropodomorph or ornithischian relatives as sometimes thought. Unlike most other theropods, therizinosaurs have four functional toes, like sauropodomorphs and some ornithischians. But Beipiaosaurus' feet, which have reduced inner toes, show that the therizinosaur condition evolved from a three-toed ancestor.

The head was relatively larger than that of other therizinosaurs, and it had some features similar to the related oviraptorosaurs.

I.    Beipiaosaurus inexpectus
II.   Enigmosaurus mongoliensis
III.  "Chilantaisaurus" zheziangensis (based on other Therizinosauria) 
IV.   Alxasaurus elesitaiensis
V.    Erlikosaurus andrewsi
VI.   Segnosaurus galbinensis
VII.  Nanshiungosaurus brevispinus (based on other Therizinosauria) 
VIII. "Nanshiungosaurus" bohlini (based on other Therizinosauria) 
IX.   Therizinosaurus cheloniformis