Thursday, June 4, 2009
First definitive carcharodontosaurid from Asia
Shaochilong maxilla (top), braincase (middle) and skull roof (bottom) from Brusatte et al., 2009.
"While in Beijing I figured I should try to see the specimen, as some authors had suggested that it was a tyrannosauroid or a basal coelurosaur of some kind. Either way, it would provide important data for my thesis. But when I opened the drawer and saw the maxilla and braincase staring back at me, I quickly realized something was wrong. “C.” maortuensis is not a coelurosaur, but possesses a number of unique features seen in Carchrodontosaurus, Giganotosaurus, Mapusaurus, and Acrocanthosaurus—colossal theropods closely related to Allosaurus that are grouped within their own subclade, the Carcharodontosauridae (the shark-toothed reptiles, named for obvious reasons)."
The new name given to this animal, Shaochilong, "meaning “shark teeth dragon” in Chinese, [is an] obvious reference to the carcharodontosaurids."
Brusatte, S., Benson, R., Chure, D., Xu, X., Sullivan, C., & Hone, D.(2009). The first definitive carcharodontosaurid (Dinosauria: Theropoda) from Asia and the delayed ascent of tyrannosaurids Naturwissenschaften DOI: 10.1007/s00114-009-0565-2
Abstract: Little is known about the evolution of large-bodied theropod dinosaurs during the Early to mid Cretaceous in Asia. Prior to this time, Asia was home to an endemic fauna of basal tetanurans, whereas terminal Cretaceous ecosystems were dominated by tyrannosaurids, but the intervening 60 million years left a sparse fossil record. Here, we redescribe the enigmatic large-bodied Chilantaisaurus maortuensis from the Turonian of Inner Mongolia, China. We refer this species to a new genus, Shaochilong, and analyze its systematic affinities. Although Shaochilong has previously been allied with several disparate theropod groups (Megalosauridae, Allosauridae, Tyrannosauroidea, Maniraptora), we find strong support for a derived carcharodontosaurid placement. As such, Shaochilong is the first unequivocal Asian member of Carcharodontosauridae, which was once thought to be restricted to Gondwana. The discovery of an Asian carcharodontosaurid indicates that this clade was cosmopolitan in the Early to mid Cretaceous and that Asian large-bodied theropod faunas were no longer endemic at this time. It may also suggest that the ascent of tyrannosaurids into the large-bodied dinosaurian predator niche was a late event that occurred towards the end of the Cretaceous, between the Turonian and the Campanian.