Thursday, June 14, 2007

Gigantoraptor erlianensis from China

A gigantic bird-like dinosaur from the Late Cretaceous of China. 2007. Xing Xu, et al. Nature 447: 844-847.

Zhao Chuang and Xing Lida/IVPP

From David Cyranoski at

The newly discovered oviraptorid Gigantoraptor erlianensis is thought to have been 8 m long, 3.5 m high at the hip and 1,400 kg in weight — 35 times as heavy as its next largest family members and 300 times the size of smaller ones such as Caudiperyx.

Comparison of the animal with other known dinosaurs — looking at more than a hundred characteristics, including limb proportions — puts Gigantoraptor firmly in the Oviraptoridae family

Gigantoraptor had long arms, bird-like legs, a toothless jaw, and probably a beak. There are no clear signs as to whether it was feathered. However, judging from its close affinity to other dinosaurs known to have been feathered, Xing Xu of the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing speculates that it was.

The animal was found by accident in April 2005, when Xu was re-enacting the find of a sauropod for a Japanese documentary film crew. While the cameras were rolling, Xu randomly picked out a bone from a dig site in the Gobi Desert, where a unique sauropod had previously been found. As he started clearing away the dirt, Xu soon realized that the bone was not from a sauropod. Its large size suggested a tyrannosaur, but he couldn't be sure. "I told them to stop filming," recalls Xu. "I said, 'This is not for your programme.'"

Abstract: An evolutionary trend of decreasing size is present along the line to birds in coelurosaurian theropod evolution, but size increases are seen in many coelurosaurian subgroups, in which large forms are less bird-like. Here we report on a new non-avian dinosaur, Gigantoraptor erlianensis, gen. et sp. nov., from the Late Cretaceous Iren Dabasu Formation of Nei Mongol, China.

Although it has a body mass of about 1,400 kg, a phylogenetic analysis positions this new taxon within the Oviraptorosauria, a group of small, feathered theropods rarely exceeding 40 kg in body mass. A histological analysis suggests that Gigantoraptor gained this size by a growth rate considerably faster than large North American tyrannosaurs such as Albertosaurus and Gorgosaurus.

Gigantoraptor possesses several salient features previously unknown in any other dinosaur and its hind limb bone scaling and proportions are significantly different from those of other coelurosaurs, thus increasing the morphological diversity among dinosaurs. Most significantly, the gigantic Gigantoraptor shows many bird-like features absent in its smaller oviraptorosaurian relatives, unlike the evolutionary trend seen in many other coelurosaurian subgroups