Dinosaur - Xiongguanlong baimoensis

Introduction

Pronounced zhong-gwan-LONG by-mo-en-sis

Xiongguanlong means ‘dragon from Xiong Guan’ in Mandarin, and baimoensis is from the Mandarin for ‘white ghost’, referring to the ‘White Ghost Castle’ formation near the fossil site.

This meat-eater was an early tyrannosaur that grew to about 5 metres long.

Identification

Xiongguanlong was a mid-sized tyrannosaur with a long narrow snout similar to that of Alioramus.

Several ‘hallmark’ features of Late Cretaceous tyrannosaurs like T. rex can be seen in the older Xiongguanlong, such as a boxy skull and midline crest at the back of the skull. It also had reduced arm length compared to earlier tyrannosaurs, but not as reduced as those of the later members of the Tyrannosauridae family. The vertebrae were more robust than in other basal tyrannosauroids, possibly to better support a big skull.

Xiongguanlong differs from early tyrannosaurs like Dilong and Eotyrannus, and later ones such as Gorgosaurus and Tyrannosaurus, in lacking serrations along the carinae (ridges) of the premaxillary (front of the upper jaw) teeth.

Full-grown adults would have weighed about 270 kilograms. Compare this with T. rex, which may have weighed as much as 9 tonnes (over 9000 kilograms).

Habitat

Other animals known to have lived in the same region and time as Xiongguanlong include turtles, therizinosauroids, ornithomimosaurs, sauropods and ornithopods.

Distribution

This species lived in western China during the Early Cretaceous, about 113-100 million years ago.

Feeding and diet

Like other tyrannosaurs, this species was a meat-eating hunter and would have preyed on small- to medium-sized animals.

The nasal area of Xiongguanlong had little transverse vaulting with little or no dorsal ornamentation. This indicates that it was not as well adapted to withstand extreme bite forces as its Late Cretaceous relatives, and may have attacked prey smaller than itself.

Fossils description

The only known fossils come from Gansu in western China, and were found in the 2000s. They were published in a paper in 2010. Fossil material includes a complete skull (but no lower jaws), all neck and back vertebrae, a partial hip bone and upper leg bone (femur).

Evolutionary relationships

Xiongguanlong is one of the links between the earlier, small-bodied tyrannosaurs, and larger, later ones. It has yet to be placed in a tyrannosaur family, but sits within the larger superfamily Tyrannosauroidea.

References

Li, Daqing; Norell, Mark A.; Gao, Ke-Qin; Smith, Nathan D.; Makovicky, Peter J. (2010). "A longirostrine tyrannosauroid from the Early Cretaceous of China". Proceedings of the Royal Society B: Biological Sciences 277 (1679): 183–190