Friday, April 6, 2012

[Paleontology • 2006] Guanlong wucaii 'crown dragon' • A proceratosaurid tyrannosauroid dinosaur from the Late Jurassic of China

An artist rendering of Guanlong wucaii, the newly discovered basal tyrannosauroid, oldest known cousin of the Tyrannosaurus rex.
Credit: Zhang Zongda/IVPP

Guanlong wucaii skull | Photo Credit: IVPP 

Guanlong wucaii skull rendering  | Photo Credit: R.S. Li, IVPP 

Theropoda Marsh, 1881
Coelurosauria von Huene, 1914

Tyrannosauroidea Osborn, 1905
Proceratosauridae Rauhut, Milner & Moore-Fay, 2010

Guanlong wucaii gen. et sp. nov.

Etymology. The generic name is derived from the Chinese Guan (crown) and long (dragon); the specific name is from the Chinese wucai (five colours), which refers to the rich colours of rocks that produced the specimens.

Holotype. IVPP (Institute of Vertebrate Paleontology and Paleoanthropology, Beijing) V14531 is a partly articulated skeleton preserving most of the elements.

Referred material. IVPP V14532 is much smaller than the holotype and is a fully articulated, nearly complete skeleton.

Locality and horizon. Wucaiwan area, Junggar Basin, Xinjiang; Oxfordian upper part of the Shishugou Formation. 

Xu X., Clark, J.M., Forster, C. A., Norell, M.A., Erickson, G.M., Eberth, D.A., Jia, C., and Zhao, Q. 2006. A basal tyrannosauroid dinosaur from the Late Jurassic of China. Nature 439 (7077): 715–718. doi:10.1038/nature04511

'Crowned dragon': This reconstruction of the head of Guanlong wucaii is based on Xu and colleagues, the most notable feature being the crest, which may have been used in visual display. 
(Drawing by Zhongda Zhang, reproduced by courtesy of the Institute of Vertebrate Paleontology and Paleoanthropology, Beijing.)

 Guanlong wucaii in evolutionary context:
The bipedal and carnivorous theropod dinosaurs first appeared around 235 million years (Myr) ago in the Triassic period, later diverging into several different lines. In particular, during the Jurassic, one lineage (the Avetheropoda) divided into the Carnosauria and Coelurosauria, the latter including the Tyrannosauroidea. Certain primitive features of the two Guanlong fossils show that Guanlong lies at the base of the lineage of the tyrannosauroids, and close to the divergence between the major lineages of coelurosaurs. Numbers in parentheses indicate adult length.

Two small Guanlong wucaii dinosaurs struggle to escape a muddy pit in what is now China during the late Jurassic period.
Illustration courtesy Michael Skrepnik

New Dinosaur Is Oldest Cousin of Tyrannosaurus Rex: