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Tianyuraptor ostromi: yet another Liaoning dromaeosaurid

This just in:

X. Zheng, X. Xu, H. You, Q. Zhao, & Z. Dong. In press. A short-armed
dromaeosaurid from the Jehol Group of China with implications for early
dromaeosaurid evolution. Proc. R. Soc. B published online before print
August 19, 2009, doi:10.1098/rspb.2009.1178


Recent discoveries of basal dromaeosaurids from the Early Cretaceous
Jiufotang and Yixian formations of Liaoning, China, add significant new
information about the transition from non-avian dinosaurs to avians. Here we
report on a new dromaeosaurid, Tianyuraptor ostromi gen. et sp. nov., from
the Early Cretaceous Yixian Formation of western Liaoning, China, based on a
nearly complete skeleton. Tianyuraptor possesses several features only seen
in other Liaoning dromaeosaurids, although to a less developed degree, and
it also exhibits features unknown in Laurasian dromaeosaurids but present in
the Gondwanan dromaeosaurids and basal avialans, thus reducing the
morphological gap between these groups. Tianyuraptor possesses a
comparatively small furcula and proportionally short forelimbs. This lies in
stark contrast to the possible capacity for flight in the microraptorines,
which have proportionally long and robust forelimbs and large furculae. The
presence of such striking differences between the Early Cretaceous Jehol
dromaeosaurids reveals a great diversity in morphology, locomotion and
ecology early in dromaeosaurid evolution. 



Beautiful skeleton with flattened skull. Falls out as closer to
Eudromaeosauria than to Unenlagiinae, in among a paraphyletic bush of other
non-eudromaeosaur, non-microraptorine Laurasian dromaeosaurids (Adasaurus,
Tsagaan, Bambiraptor); depending on which of the most parsimonious trees you
look at, it is either a basal microraptorine or a basal member of
everybody-but-Microraptorinae. Looks to be about 1.75 m long.

Thomas R. Holtz, Jr.
Email: tholtz@umd.edu   Phone: 301-405-4084
Office: Centreville 1216                        
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
Fax: 301-314-9661               

Faculty Director, Earth, Life & Time Program, College Park Scholars
Faculty Director, Science & Global Change Program, College Park Scholars
Fax: 301-314-9843

Mailing Address:        Thomas R. Holtz, Jr.
                        Department of Geology
                        Building 237, Room 1117
                        University of Maryland
                        College Park, MD 20742 USA