Dinosaur - Guanlong wucaii

Introduction

Pronounced GWON-long woo-kay-eye

Named from the Chinese words guan, meaning 'crown', and long, meaning 'dragon', in reference to its flashy head-crest, the most elaborate of any known theropod dinosaur. The species name comes from the Chinese word wucai meaning 'five colours' and refers to the multi-hued rocks at Wucaiwan, the badlands where the fossils were found.

Guanlong wucaii is one of the most primitive tyrannosaurs known. It hunted its prey 95 million years before T. rex lived.

Identification

Guanlong wucaii was a small to mid-sized early tyrannosaur and a member of the family Proceratosauridae.

Guanlong wucaii wasn’t your typical tyrannosaur; it has long arms and three-fingered hands for grabbing and ripping. But the shape of its teeth, and features in the skull and pelvis place it in the tyrannosauroid superfamily. Like many other theropods, it almost certainly had feathers.

Guanlong's head crest ran along its snout, from nostrils to eye sockets. It was distinctly delicate (about as thin as a tortilla and only 5-6 cm high), too flimsy for use as a weapon, and probably brightly coloured. Made from fused nasal bones, the crest was filled with air sacs and reminded the discoverers of the ornamental features found on some living birds, like cassowaries and hornbills. The crest may have been attractive to other Guanlong. Such a showpiece is unusual in a predator.

Habitat

Guanlong hunted in a forested environment, predominantly made up of conifers and a variety of ferns, including giant forms. The climate was seasonal, with warm and humid summers and dry winters. The forest and river system supported other fauna including turtles, small mammals, and dinosaurs such as large sauropods, ornithopods, and small and large theropods.

Distribution

The first Guanlong fossils were found in 2002, and described and named in 2006.

One of the earliest tyrannosauroids yet to be discovered, Guanlong roamed what is now Xinjian, China, during the Late Jurassic Period, 163-158 million years ago.

Feeding and diet

Guanlong hunted smaller dinosaurs, mammals and other animals. It may also have been a meal itself for larger predators like the allosaur Yangchuanosaurus.

Fossils description

The fossils of two Guanlong were discovered by T Yu in 2002 in the Shishugou Formation at Wucaiwan, Junggar Basin, Xinjiang, in north-western China, and have been dated to 163-158 million years old (Late Jurassic). They were then described in 2006 by Xu Xing and Dr James M Clarke of George Washington University. The holotype (the specimen used to describe the species) consists of a reasonably complete and partially articulated adult skeleton. The second specimen is a fully articulated, nearly complete skeleton, though much smaller than the holotype.

The two known specimens died in the same way and in the same place: they fell into the muddy footprint of a massive herbivore (probably the sauropod Mamenchisaurus) and were trapped. The 6-year-old died first and was probably trampled by the adult, who arrived later. Both skeletons are almost complete.

The original skeleton is held at the Institute of Vertebrate Paleontology and Paleoanthropology in China. The Australian Museum has a life-size reconstruction of the adult.

Evolutionary relationships

Like other early theropods, Guanlong was relatively small and only a fraction as large as later tyrannosaurids such as Tyrannosaurus rex.

The skeletal differences between earlier and later tyrannosaurs suggest that Guanlong was an intermediate step in evolution between early primitive coelurosaurs (a theropod group that tyrannosaurs belong to) and and later, larger tyrannosaurids.

Guanlong belongs to the family Proceratosauridae, which includes other tyrannosauroids Kileskus, Proceratosaurus and Sinotyrannus.

Further reading

A basal tyrannosauroid dinosaur from the Late Jurassic of China; Xing Xu, James M. Clark, Catherine A. Forster, Mark A. Norell, Gregory M. Erickson, David A. Eberth, Chengkai J & Qi Zhao. Nature volume 439, pages 715–718(2006)