Thursday, May 30, 2013

[Paleontology • 2013] Aurornis xui | “daybreak bird” • A Jurassic avialan dinosaur from China resolves the early phylogenetic history of birds



Reconstruction of Aurornis xui,
a new basal avialan from the Middle/Late Jurassic of China.

illustration: Masato Hattori

The recent discovery of small paravian theropod dinosaurs with well-preserved feathers in the Middle–Late Jurassic Tiaojishan Formation of Liaoning Province (northeastern China) has challenged the pivotal position of Archaeopteryx regarded from its discovery to be the most basal bird. Removing Archaeopteryx from the base of Avialae to nest within Deinonychosauria implies that typical bird flight, powered by the forelimbs only, either evolved at least twice, or was subsequently lost or modified in some deinonychosaurians. Here we describe the complete skeleton of a new paravian from the Tiaojishan Formation of Liaoning Province, China. Including this new taxon in a comprehensive phylogenetic analysis for basal Paraves does the following: (1) it recovers it as the basal-most avialan; (2) it confirms the avialan status of Archaeopteryx; (3) it places Troodontidae as the sister-group to Avialae; (4) it supports a single origin of powered flight within Paraves; and (5) it implies that the early diversification of Paraves and Avialae took place in the Middle–Late Jurassic period.


Holotype: Aurornis xui 
 Thierry Hubin/IRSNB

Theropoda Marsh, 1881
Maniraptora Gauthier, 1986
Paraves Sereno, 1997
Avialae Gauthier, 1986

Aurornis xui gen. et sp. nov.

Etymology. Aurora, Latin for daybreak, dawn; Ornis, Greek for bird; xui, in honour of Xu Xing, for his exceptional and continuing contribution to our understanding of the evolution and biology of feathered dinosaurs.

Holotype. Yizhou Fossil and Geology Park (YFGP)-T5198, a complete articulated skeleton with associated integumentary structures.

Locality and horizon. Yaolugou, Jianchang, western Liaoning Province, China; Middle–Late Jurassic Tiaojishan Formation (see Supplementary Information).

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New Bird-Like Dinosaur Settles Origins of Flight 
A new species found in China has shed light on the answer. The two-foot long Aurornis xui, the “daybreak bird,” fleshes out the relationships between bird-like dinosaurs and, along with its cousin species Archaeopteryx and Anchiornis, restores its lineage as the likely predecessors of birds.
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http://bit.ly/118FJ9F  via @DiscoverMag



Pascal Godefroit, Andrea Cau, Hu Dong-Yu, François Escuillié, Wu Wenhao & Gareth Dyke. 2013. A Jurassic avialan dinosaur from China resolves the early phylogenetic history of birds. Nature. doi: dx.doi.org/10.1038/nature12168

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