Guanlong

Phylogeny: Dinosauria > Saurischia > Theropoda > Neotheropoda > Tetanurae > Avetheropoda > Coelurosauria > Tyrannosauroidea > Proceratosauridae

Overview: By the end of the Cretaceous, the tyrannosaurs had become the dominant land predators of the northern hemisphere, mainly in Asia and North America. They had also obtained considerable size, with Tyrannosaurus itself being among the largest known theropods. However, the tyrannosaur lineage had humble beginnings. They first appear in the fossil record during the Middle Jurassic. Guanlong itself lived towards the start of the Late Jurassic and, like most of its early tyrannosaur relatives, it wasn’t overly large. In terms of length, Guanlong was about three or four meters long at most and lightly built, quite unlike the tyrannosaur bruisers that would evolve some fifty to sixty million years later. Scientists usually classify Guanlong within a family known as the Proceratosauridae, which contained some of the most basal and earliest known members of the tyrannosauroid superfamily. Despite their name, they weren’t close relatives of Ceratosaurus.

Proceratosaurids shared a few features in common that set them apart from their later relatives, in addition to their (typically) smaller size. The earliest tyrannosaurs had rather long arms and retained three distinct, clawed digits on each hand. Fragile, bony head crests were also common to the proceratosaurids, growing along their snouts. Guanlong itself possessed such a crest, which took on a rounded form and was probably used for visual display. The creature’s name actually refers to this feature, being derived from the Mandarin Chinese words for “crown” and “dragon”. Guanlong fossils are known from China’s Shishugou Formation, located in what is now the western territory of Xinjiang. Like other Jurassic tyrannosaurs, Guanlong lived in the shadow of much larger predators. In its case, this was likely the allosauroid Sinraptor or the more basal Monolophosaurus. Guanlong probably occupied a niche pursuing smaller prey than either dinosaur.