1 Nature 2012 Vol: 484(7392):92-95. DOI: 10.1038/nature10906

A gigantic feathered dinosaur from the Lower Cretaceous of China

Numerous feathered dinosaur specimens have recently been recovered from the Middle-Upper Jurassic and Lower Cretaceous deposits of northeastern China, but most of them represent small animals. Here we report the discovery of a gigantic new basal tyrannosauroid, Yutyrannus huali gen. et sp. nov., based on three nearly complete skeletons representing two distinct ontogenetic stages from the Lower Cretaceous Yixian Formation of Liaoning Province, China. Y.[thinsp]huali shares some features, particularly of the cranium, with derived tyrannosauroids, but is similar to other basal tyrannosauroids in possessing a three-fingered manus and a typical theropod pes. Morphometric analysis suggests that Y.[thinsp]huali differed from tyrannosaurids in its growth strategy. Most significantly, Y.[thinsp]huali bears long filamentous feathers, thus providing direct evidence for the presence of extensively feathered gigantic dinosaurs and offering new insights into early feather evolution.

Editor's summary

T. rex's giant feathered friends Tyrannosaurus rex and its gigantic cousins lived at the close of the Cretaceous period, around 70 million years ago. Earlier relatives were thought to have been much smaller than T. rex, but recent finds from the early Cretaceous of China have had body lengths of up to 10 metres. Three 125-million-year-old specimens of a new tyrannosauroid species from China add a twist to this story: not only were the creatures large (the adult may have weighed around 1,400 kg), but they were also feathered. This basal tyrannosauroid is the largest feathered creature known, living or extinct, and raises interesting questions about dinosaur development and metabolism.

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Figures
Figure 1: Yutyrannus huali (ZCDM V5000 and ZCDM V5001). a, Photograph of the slab preserving ZCDM V5000 and ZCDM V5001. b, Line drawing of the slab. Abbreviations: cav, caudal vertebra; cev, cervical vertebra; dr, dorsal rib; dv, dorsal vertebra; ga, gastralia; lfe, left femur; lfi, left fibula; lh, left humerus; lil, left ilium; lis, left ischium; lm, left manus; lp left pes; lr, left radius; ls, left scapula; lt, left tibiotarsus; lu, left ulna; ma, mandible; pu, pubis; rc, right coracoid; rfe, right femur; rh, right humerus; ril, right ilium; rm, right manus; rp, right pes; rr, right radius; rs, right scapula; rt, right tibiotarsus; ru, right ulna; sk, skull; sy, synsacrum. Figure 2: Selected elements of Y. huali (ZCDM V5000, ZCDM V5001 and ELDM V1001). a, Photograph of the skull and mandible of ELDM V1001. b, Line drawing of the skull and mandible of ELDM V1001. c–h, filamentous integumentary structures preserved in the three specimens: c, along the posterior caudal vertebrae of ZCDM V5000; d, along the cervical vertebrae of ELDM V1001; e, f, along a limb bone of ELDM V1001; g, h, near the pes of ZCDM V5001 (f and h are close-up views). Abbreviations: aop, accessory orbital process; clp, cultriform process; co, concavity; cp, cornual process; g, groove; lec, left ectopterygoid; lpa, left palatine; ls, left squamosal; mf, maxillary fenestra; np, nasal prominences; pnr, pneumatic recesses; r, ridge; sp., suborbital process; sr, surangular ridge. Figure 3: A simplified cladogram showing the systematic position of Y. huali among the Tyrannosauroidea. Silhouettes indicate body size and possible extent of plumage. Different tyrannosauroids seem to have attained gigantic body size independently in the Early and Late Cretaceous, but only in the Early Cretaceous is there direct evidence of a gigantic form with an extensively feathered integument. This may reflect the relatively cold climate of the middle Early Cretaceous. See also Supplementary Information.
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References
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    • . . . The forelimbs are also similar to those of basal tyrannosauroids in retaining a typical basal coelurosaurian design, including a three-fingered manus15. . . .
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    • . . . Y. huali lived during a period (the Barremian–early Albian) that has been interpreted as considerably colder than the rest of the Cretaceous (a mean annual air temperature of about 10 °C in western Liaoning, in contrast with about 18 °C at a similar latitude in the Late Cretaceous)27 . . .
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    • . . . Most gigantic Late Cretaceous tyrannosauroids, by contrast, lived in a warm climate that was conducive to the loss of an extensive insulative feathery covering, although populations inhabiting cold environments such as the land that is now Alaska would have been a notable exception28, 29 . . .
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    • . . . It is possible that the extent and nature of the integumentary covering changed over time in response to shifts in body size and the temperature of the environment throughout tyrannosauroid evolutionary history, as has clearly occurred in some mammalian taxa30 . . .
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