A new dromaeosaur from wetern Liaoning

["高橋 和男" <pantheon@dino-pantheon.com>]

A NEW DROMAEOSAUR (DINOSAURIA: THEROPODA) FROM THE EARLY
CRETACEOUS YIXIAN FOMATION OF WESTERN LIAONING
XU Xing, WANG Xiao-Lin
VERTEBRATA PALASIATICA vol.42 No.2 pp.111-119

Abstract
A specimen collected from the Early Cretaceous lowest part
of Yixian Formation of Liaoning, northeastern China, represents
a new genus and species of dromaeosaurid theropod.
It comprises a fragmentary maxilla with some teeth, a few 
caudals, almost complete fore limbs, and partial hind limbs
and is here named Graciliraptor lujiatunensis gen. et. sp. nov.
Distinctive characteristics of the new species include a laminal 
 structure connecting the postzygapophyses of middle caudals,
middle caudals extremely long and slender,small manual ungual I, proximal end 
of metacarpal III strongly expanded, proximal 
tibiotarsus shaft rectangular in cross section, astragalar medial condyle 
significantly expanded posteriorly, metatarsal II 
distally much wider than the other metatarsals and long and 
slender pedal phalanx III-1.
Being the earliest definitive dromaeosaurid species known to date,
G. lujiatunensis provides new information important for 
undrstanding the early evolution of the group.
On one hand, G. lujiatunensis displays a few features similar
 to those of basal birds, such as caudals significantly elongated, semilunate 
carpal small and primalily contacting metacarpal II, 
and manual digit I short, providing further evidence for a close rlationship 
between the Dromaeosauridae and the Aves; on the other
 hand, it is similar to troodontids in some features on the caudals.
The discovery of G. lujiatunensis also indicates a high diversity 
of the Dromaeosaridae in the Early Cretaceous Jehol Biota.
Combined with other lines of evidence, it is inferred that the
Dromaeosaridae rapidly diversified taxonomically but remained
relatively stable morphologically in the early evolution of the
group. 



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TAKAHASHI, Kazuo 高橋　和男
pantheon@dino-pantheon.com
http://www.dino-pantheon.com/
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