Beipiaosaurus

Phylogeny: Dinosauria > Saurischia > Theropoda > Neotheropoda > Tetanurae > Avetheropoda > Coelurosauria > Maniraptora > Therizinosauria > Therizinosauroidea

Overview: Therizinosaurs were among the most bizarre of the theropod lineages. Members tended to be semi-upright in their posture, had enlarged fourth toes, enormous arms, sickle-shaped claws and, for the most part, were entirely herbivorous. Beipiaosaurus itself belonged to this unusual lineage, being one of the earlier confirmed therizinosaurs. It belonged to the superfamily Therizinosauroidea, which made it more derived than some earlier therizinosaurs, such as Falcarius, but it fell outside the family Therizinosauridae. Therizinosaurids were more derived and usually larger than Beipiaosaurus, tending to have the most exaggerated of the above listed features. Its posture wasn’t as upright, the neck a bit shorter, its head proportionately larger, and its overall body size was smaller. However, it did possess the long arms, enlarged claws and herbivorous diet of its later relatives.

Beipiaosaurus lived in the Early Cretaceous, in what is now the northeast of China. This region had a temperate or at most subtropical climate at that time, with landscapes of dense woodlands and lakes, dotted by active volcanoes. Beipiaosaurus ate mostly low to mid-level vegetation, using its long claws to manipulate branches, but also to defend itself against attackers. Fossils of the animal were first recovered in the mid-1990’s, from the famed Yixian Formation. Like many fossils found in the Yixian, its holotype specimen preserved extensive feather impressions (volcanic sediments are good for preserving such features). Prior to the discovery of Yutyrannus, Beipiaosaurus was for a time the largest dinosaur known with certainty to have had feathers. In its case, these were fairly basic, hair or ribbon-like proto-feathers, which would’ve been useful for insulating its body. Described in 1999, its name refers to the Chinese city of Beipiao.