Yutyrannus huali

Yutyrannus huali was a giant early tyrannosauroid from the Yixian Formation of northeastern China. Three skeletons preserve patches of simple filamentous feathers on the neck, body, arms and tail, providing direct evidence that a very large non-avian dinosaur could carry an extensive feathery covering. Yutyrannus lived long before the deep-skulled, two-fingered tyrannosaurids of the Late Cretaceous and retained a longer, lower skull, three-fingered hands and comparatively long arms. Its discovery did not prove that every adult tyrannosaur was equally feathered, but it greatly widened the known body-size range of directly feathered dinosaurs.

Its fossils occur between approximately 125.8 and 124.1 million years ago. Values shown here are approximate and reflect the current curated seed dataset.

The largest skeleton approached nine metres in length and was estimated at roughly 1.4 tonnes. Its skull carried a low midline crest and additional ridges above and in front of the eyes. The jaws held recurved serrated teeth, while each relatively long forelimb ended in three clawed fingers. Filamentous feathers reached about 15 to 20 centimetres in some preserved patches. These structures were simpler than the vaned flight feathers of birds and were probably useful for insulation and display rather than flight.

• Long filamentous feathers preserved on several body regions
• Low cranial crest and paired ridges around the eyes
• Longer, lower skull than later tyrannosaurids
• Three clawed fingers on each hand
• Recurved, serrated predatory teeth
• Long balancing tail and powerful hind limbs

Xing Xu and colleagues named Yutyrannus huali in 2012 from three nearly complete skeletons obtained from the same fossil-bearing horizon in western Liaoning. The holotype is ZCDM V5000; ZCDM V5001 and ELDM V1001 represent an additional adult-sized animal and a smaller individual. The fossils came from the Lower Cretaceous Yixian Formation and preserve two growth stages. Their close association is noteworthy, but the specimens alone cannot establish coordinated pack hunting or a permanent social group.

Discovery credit: Local fossil collectors and the Xu Xing research team.

Naming authors: Xing Xu, Kebai Wang, Ke Zhang and 6 coauthors.

The Yixian Formation records lakes, forests and volcanically active landscapes within the Jehol Biota. It preserves conifers, flowering plants, fish, amphibians, mammals, pterosaurs, birds and many feathered dinosaurs. Geochemical evidence indicates a cool temperate climate by Cretaceous standards, making insulation a plausible benefit of Yutyrannus's filamentous coat, although display may also have mattered.

Its teeth, skull and body plan identify Yutyrannus as a large terrestrial predator. The three known animals came from one quarry and horizon, but this could reflect behaviour, a shared death event or transport and burial processes. No trackway, nest or bite-mark evidence demonstrates pack hunting. The feathers probably contributed to insulation and may also have made the head crest and body outline more conspicuous during display.

• It remains one of the largest dinosaurs with direct fossil evidence of feathers.
• All three named specimens are unusually complete and represent at least two growth stages.
• Its hands still had three functional fingers, unlike later tyrannosaurids.
• The name combines Mandarin for feather with the Latin tyrannus and Chinese huali, meaning beautiful.

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   A gigantic feathered dinosaur from the Lower Cretaceous of China

   Xing Xu, Kebai Wang, Ke Zhang and 6 coauthors · Nature 484 · 2012

   Open source