Guanlong wucaii

Guanlong wucaii was an early tyrannosauroid that lived roughly ninety million years before Tyrannosaurus. Two skeletons preserve both adult and juvenile anatomy, revealing a lightly built, long-armed predator unlike the massive, two-fingered tyrannosaurids of the Late Cretaceous. Its most conspicuous feature was a large, thin crest along the skull midline. The crest was poorly suited to resisting force and is therefore commonly interpreted as a visual display structure, although its colour and social meaning remain unknown.

Its fossils occur between approximately 161.2 and 159.7 million years ago. Values shown here are approximate and reflect the current curated seed dataset.

Guanlong had a long, low skull armed with small serrated teeth and topped by a thin crest built mainly from the nasal bones. Large openings and delicate struts reduced the crest's mass. The adult had a proportionally larger, more elaborate crest than the juvenile. Its forelimbs remained long and ended in three functional fingers, while long hind limbs and a balancing tail supported bipedal locomotion. A coat of simple filamentous feathers is plausible from related tyrannosauroids but is not preserved with either Guanlong skeleton.

• Tall, thin midline crest extending along the snout and skull roof
• Long forelimbs with three functional fingers
• Lightly built skull with small serrated teeth
• Long hind limbs suited to bipedal locomotion
• Adult and juvenile skeletons documenting growth
• Early proceratosaurid tyrannosauroid anatomy

A joint Institute of Vertebrate Paleontology and Paleoanthropology–George Washington University expedition recovered two individuals from the Shishugou Formation at Wucaiwan in 2002. Xu Xing and seven coauthors named them in Nature in 2006. The holotype IVPP V14531 is a partly articulated adult, while IVPP V14532 is a more complete juvenile. Guanlong means crowned dragon; wucaii refers to the multicoloured badlands of Wucaiwan rather than the dinosaur's colour.

Naming authors: Xu Xing, James M. Clark, Catherine A. Forster and 5 coauthors.

The upper Shishugou Formation at Wucaiwan records a seasonally dry landscape crossed by rivers and dotted with wetlands and volcanic deposits. Guanlong shared the region with sauropods, small ornithischians and other theropods. Some vertebrate skeletons accumulated in deep mud-filled depressions, but the two Guanlong individuals do not establish that the species hunted or lived socially.

Its teeth and agile theropod proportions identify Guanlong as a predator of comparatively small animals. The fragile cranial crest was probably more useful for visual signalling than combat, but no fossil reveals display posture, sex differences or crest colour. The adult and juvenile specimens provide growth information, not evidence of parental care or a family group.

• Guanlong lived about ninety million years before Tyrannosaurus rex.
• The adult's crest was proportionally larger and more elaborate than the juvenile's.
• It retained three useful fingers instead of the reduced two-fingered hand of later tyrannosaurids.
• The species name refers to colourful rocks at the fossil site, not preserved body colour.

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1. 01
   A basal tyrannosauroid dinosaur from the Late Jurassic of China

   Xu Xing, James M. Clark, Catherine A. Forster and 5 coauthors · Nature 439, 715–718 · 2006

   Open source
2. 02
   The cranial osteology and phylogenetic position of the theropod dinosaur Proceratosaurus bradleyi from the Middle Jurassic of England

   Oliver W. M. Rauhut, Angela C. Milner, Scott Moore-Fay · Zoological Journal of the Linnean Society 158(1), 155–195 · 2010

   Open source