Guanlong
Guanlong is an extinct genus of early tyrannosaur that lived about 160 million years ago, during the Late Jurassic period, in what is now northwestern China. Its name means "crown dragon" - referring to the tall crest on its head. Guanlong is one of the earliest known members of the tyrannosaur lineage, long before famous giants like Tyrannosaurus rex. Its fossils show what tyrannosaurs were like when they were still small, lightly built hunters rather than the huge apex predators they later became.
Currently, one known species exists - Guanlong wucaii. The fossils of Guanlong were found in the Dzungaria region of Xinjiang, China, in rocks belonging to the Shishugou Formation. The name of the species, wucaii, refers to the multicoloured rocks of the Wucaiwan area where it was discovered. Two individuals are currently known: a nearly complete juvenile and a partially complete adult.
Discovery Site
Both skeletons were found one on top of the other, along with the remains of other dinosaurs, in what scientists call a "death pit". These were natural depressions or sinkholes that formed in soft ground. Animals that wandered in could become trapped, either sinking into mud or falling into a pit they could not climb out of. Over time, more animals could fall in, leading to several skeletons being buried together. This kind of deposit provides an unusual opportunity to study different individuals of the same species in one place.
Appearance and Build
Guanlong was a slender, two-legged predator around 3 - 3.5 m long, 1 m tall, and weighing about 125 kg. It was far smaller than its later relatives, which could grow to over 10 m and weigh several tonnes.
It had a long tail for balance and long arms with three fingers on each hand. This is important because it shows that the tiny, two-fingered arms of later tyrannosaurs evolved later in the group's history. Its humerus (upper arm bone) was more than 60% of the length of its thigh bone, which is quite large compared to most later tyrannosaurs.
Its body proportions and light build suggest it was a fast and active hunter, preying on smaller animals or scavenging. Guanlong is also thought to have had simple, hair-like feathers, similar to those found on its close relative Dilong, although no direct feather impressions have been found with its fossils.
The Crest
The most striking feature of Guanlong was its tall, narrow crest running along the top of its snout and skull. The crest was made of fused nasal bones and four thin supporting ridges. It was extremely delicate - only about 1.5 mm thick in places - and contained air spaces inside. Because it was so thin, it was not suited to fighting or defence.
Instead, the crest likely served as a display structure, used for attracting mates or signalling to other members of the species. This kind of visual feature is common in many animals today, from birds to lizards. Other meat-eating dinosaurs such as Dilophosaurus and Monolophosaurus also had crests, but these species are not closely related to Guanlong. This suggests the crest of Guanlong evolved separately - an example of convergent evolution, where similar features appear in different groups because they serve a similar purpose.
Growth and Development
Because both an adult and a juvenile Guanlong were found, scientists have been able to study how it changed as it grew. The juvenile had a shorter snout, a smaller crest that was restricted to the front of the head, and longer lower legs and hands relative to its body. The adult had a taller and more extensive crest, and its proportions shifted toward a more mature shape.
Bone studies show that the juvenile died at around six years old and the adult at about twelve. The adult had already stopped growing, while the juvenile was still developing.
Habitat and Lifestyle
Guanlong lived during the Oxfordian stage of the Late Jurassic, in what is now the Shishugou Formation. At that time, the area was a floodplain with rivers, soft ground, and patches of forest. This environment supported a diverse community of animals, including other theropod (meat-eating) dinosaurs, plant-eating sauropods, early mammals, and crocodile-like reptiles.
Unlike the massive tyrannosaurs that came tens of millions of years later, Guanlong was not at the top of the food chain. Larger predators would have dominated the region, and Guanlong likely hunted smaller prey or scavenged when the opportunity arose.
Place in Tyrannosaur Evolution
Guanlong is part of a group of early tyrannosaurs sometimes called proceratosaurids - early members of the family tree that eventually produced Tyrannosaurus rex. Tyrannosaurs didn't start out as giants; for much of their history, they were small to medium-sized predators living in the shadow of bigger carnivores. Guanlong helps show what they were like in this earlier stage.
Scientists now see Guanlong and its close relatives as an early branch near the base of the tyrannosaur family tree. In other words, it lived before many of the features associated with tyrannosaurs - such as massive size, short arms, and deep, heavy skulls - had evolved.
References & Attributions
Image: Artist's depiction of Guanlong - Conty, CC BY-SA 3.0, via Wikimedia Commons
Image: Guanlong wucaii head showing the crest - チャンネルD - ChDinosaurs, CC BY-SA 4.0, via Wikimedia Commons
Image: Sizes of the adult and juvenile Guanlong specimens compared to a human - SirBlameson, CC BY-SA 4.0, via Wikimedia Commons
