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Beipiaosaurus

Beipiaosaurus inexpectus is a therizinosauroid, a part of a bizarre group of theropod dinosaurs. The discovery of Beipiaosaurus (bay-peow-SAWR-us), which means "Beipiao reptile", was announced in the May 27, 1999, concern of the journal Nature. These fossils were found in Liaoning Province, China and have been dated to the Middle Cretaceous time, about 125 million years ago. A significant number of fossilized bones for this species were improved, including: cranial fragments, a mandible, three cervical vertebrae, four dorsal vertebrae, a caudal vertebra, the scapula and scapulacoracoid, a complete forelimb, and a whole pelvis with hind limb.

The exact classification of therizinosaurs has in the past been passionately debated, since their prosauropod-like teeth and body structure indicate that they were generally herbivorous, unlike classic theropods. Beipiaosaurus, being considered to be a primitive therizinosauroid, has features which propose all therizinosauroids, including the more derived Therizinosauridae, to be coelurosaurian theropods, not sauropodomorph or ornithischian relatives as once alleged. Beipiaosaurus measured 2.2 meters (7.3 ft) in length and .88 meters (2.9 ft.) tall at the hip, and is among the largest known feathered dinosaurs. Its weight is estimated as about 85 kg (187 lbs.)

Beipiaosaurus had a toothless beak with cheek teeth. Therizinosauridae have four functional toes, but Beipiaosaurus' feet have reduced inner toes, viewing that the derived therizinosaurid condition may have evolved from a three-toed therizinosauroid ancestor. The head was relatively larger than that of other therizinosaurs, and it had some features similar to the associated Oviraptorosauria (perhaps the sister group). The fossil's skin impressions indicate its body was covered by downy feather-like fibers (protofeathers), which are very similar to those of Sinosauropteryx. As only theropod dinosaurs are so far known to have been feathered, this discovery is further evidence that therizinosaurs were indeed theropods.