Yutyrannushuali

Overview: Before tyrannosaurs took over the northern hemisphere in the Late Cretaceous, Early Cretaceous Earth was mostly ruled by a clade of allosaurs called Carcharodontosaurs. In most parts of the world, tyrannosaurs were small to medium sized beasts. However, 125 million years ago in China, a new contender had arrived, Yutyrannus, one of the first tyrannosaur apex predators. But this creature was different from the tyrannosaurs which would later rule the Late Cretaceous. While they were mostly members of the family Tyrannosauridae, Yutyrannus belonged to an earlier family of tyrannosaurs, the proceratosaurids. And like smaller proceratosaurids, Yutyrannus was fully feathered, possibly one of the largest dinosaurs to be so, and the largest dinosaur for which feathers are confirmed. It’s temporal range, large size, feathers, and the completeness of its specimens give paleontologists a rare “high-definition” glimpse into the biology and evolution of the tyrannosaurs from a time where these soon-to-be tyrants were still mostly small and sparse.

Discovery: Yutyrannus was discovered in Batu Yingzi in Liaoning Province, China in a layer of the Early Cretaceous Yixian Formation. Three specimens were discovered. The holotype (ZCDM V5000) is a mostly complete skeleton of an adult. The other two specimens (ZCDM V5001 and ELDM V1001), designated as paratypes, are from juveniles, the smallest (ELDM V1001) estimated to have been 8 years younger than the holotype. Yutyrannus huali was named and scientifically described in 2012 by Chinese paleontologist Xu Xing and colleagues. The name comes from Mandarin Chinese yǔ ("feather") and Greek tyrannos ("tyrant"), a reference to its feathers and its classification as a tyrannosauroid. The specific name is Mandarin for “beautiful”, in reference to the perceived beauty of the plumage. So its full name means “Beautiful Feathered Tyrant”.

Evolution: Yutyrannus was a member of the family Proceratosauridae in the larger clade Tyrannosauridae, and as such it was a distant cousin of Tyrannosaurus rex. Tyrannosauroids date back to the Middle Jurassic, and proceratosaurids were possibly the earliest members of the group, represented by the likes of the English Proceratosaurus and the Chinese Guanlong in their early times. In the Jurassic, these theropods were only barely cracking “medium-sized” (by theropod standards), but by 125 million years ago in the Early Cretaceous, Yutyrannus became the first known tyrannosaur to experiment with truly large size, growing to about the same size as many Late Cretaceous tyrannosaurids, like Gorgosaurus.

Description: Yutyrannus was a large tyrannosaur which grew to be 7.5-9 m (25-30 ft) in length and 1.1-1.41 tonnes (1.21-1.56 US tons) similar in size to many later-Cretaceous tyrannosaurids. As a proceratosaurid tyrannosaur, it had a fairly typical theropod body plan, with a large head, bipedal stance, and hand hands with three fingers (two-fingered tyrannosaurids wouldn’t evolve until later). Like other tyrannosaurs it had proportionally long legs adapted for running. And like some other proceratosaurids, it had a nasal crest, though this crest was much less prominent than the elaborate crests of Proceratosaurus and Guanlong. Perhaps Yutyrannus’s most famous feature is its feathers. While feathered theropods are nothing new to paleontology in the 21st Century, finding feathers on such a large animal is rather unique. Most skin impressions from large dinosaurs show scales, indicating that they either lacked feathers or that any feathers they did have were fine and sparse enough to not leave impressions. Skin impressions from tyrannosaurids are scaley, and it is thought that going featherless may have helped these large warm-blooded animals keep cool in warm climates. But feathers on Yutyrannus, which was in the same size range of most tyrannosaurids, potentially complicates our understanding. However, the environment of the Yixian Formation where Yutyrannus lived was much cooler than other Mesozoic environments, and thus the cooler temperatures of this region may have made keeping its feathers advantageous, whereas if it had lived in a warmer climate, perhaps it too would have evolved toward losing its feathers like its later relatives.

Behavior and Ecology: Yutyrannus probably lived about 125 million years ago in the Yixian Formation, though because of the fossils’ uncertain provenance, it is uncertain precisely with which animals they coexisted. Psittacosaurus, Dongbeititan, Sinosauropteryx, and Caudipteryx, and the smaller proceratosaurid Dilong all may have been among the dinosaurs, and potential prey, in Yutyrannus’s environment. The Yixian Formation seems to have been a lush temperate conifer forest with abundant lakes and volcanoes. It may have resembled the modern-day temperate rainforests of British Columbia, and probably experienced large seasonal swings in temperature, with mild summers and cold winters. The feathers of Yutyrannus would have been especially useful during the colder part of the year.

Because the three specimens of Yutyrannus were found together, its discoverers interpreted it as a pack hunter, sauropod remains from the same quarry were cited as evidence that Yutyrannus was hunter of sauropods such as Dongbeititan. Pack hunting has also been hypothesized for some other sauropod-hunting theropods, and it has been hypothesized for some tyrannosaurids as well. However, all that can be said for certain is that the animals came to be buried near each other, and we cannot say for certain whether or not they lived together. While social behavior is a possibility, it should also be noted that pack-hunting is also extremely rare among living birds and reptiles, thus casting a degree of doubt on this interpretation.

Extinction and Legacy: It is unknown why Yutyrannus went extinct. It probably wasn’t part of any mass extinction, rather it would have been a casualty of the endless cycle of evolution and extinction. By 120 million years ago, another large proceratosaurid, Sinotyrannus, had appeared in China, and it may have replaced Yutyrannus, if it wasn’t in fact descended from Yutyrannus itself. Today Yutyrannus can be found in the Zhucheng Dinosaur Museum in Zucheng, China, and the Erlianhaote Dinosaur Museum in Erenhot, China.

Yutyrannus FAQ

Yutyrannus size / How big was Yutyrannus?

See height, weight, and length.

Yutyrannus weight / How much did Yutyrannus weigh?

Yutyrannus probably weighed about 1.1-1.41 tonnes (1.21-1.56 US tons).

How long was Yutyrannus?

Yutyrannus is thought to have grown somewhere around 7.5-9 m (25-30 ft) long as an adult.

What did Yutyrannus eat?

Yutyrannus ate meat, almost certainly other dinosaurs, and perhaps with a preference for sauropods like Dongbeititan.

What is Yutyrannus’s closest living relative?

Like all dinosaurs, the closest relatives of Yutyrannus are the only surviving lineage of dinosaurs today, the birds. Crocodilians, while not dinosaurs themselves, are also more distant cousins of dinosaurs.

Yutyrannus family members / Yutyrannus family / What kind of dinosaur was Yutyrannus?

Yutyrannus was a theropod (two-legged, mainly carnivorous dinosaurs) in the family Proceratosauridae, in the clade Tyrannosauroidea, making it a distant cousin of the much larger and more famous Tyrannosaurus rex! It was especially closely related to the smaller proceratosaurid Guanlong.

Where did Yutyrannus live? / Where was Yutyrannus found?

Yutyrannus lived in what is now China.

When did Yutyrannus live?

Yutyrannus lived about 125 million years ago in the Early Cretaceous Period.

What does Yutyrannus mean? / Yutyrannus name meaning

Yutyrannus means “Feathered Tyrant”.