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A long-tailed bird with a pygostyle
Lü, Junchang & Lianhai Hou, 2005. A possible long-tailed bird with a
pygostyle from the late Mesozoic Yixian Formation, western Liaoning, China.
Acta Geologica Sinica 79 (1): 7-10.
Abstract: An incomplete caudal vertebral series (IVPP V11309) from the
Yixian Formation of late Mesozoic, Jianshangou area of Beipiao, western
Liaoning Province, may represent a new bird. The tail is composed of at
least 12 free caudal vertebrae and the most distal 5 caudal vertebrae
co-ossified into a pygostyle. The pygostyle is plate-like and slightly
curved dorsally. The anterior free caudals are amphiplatyan. The anterior
caudal surfaces of the last three free caudals are concave, but their
posterior articular surfaces are convex. The pygostyle is regarded as the
first appeared flight apparatus during the evolutionary process from
*Archaeopteryx* to neornithes. The pygostyle appeared in most early fossil
birds and almost all the modern birds. Although their morphologies are
different, they are basically formed by at least four last caudal vertebrae.
The specimen V11309 is regarded as a bird rather than a non-avian theropod
dinosaur based on the following characters: short caudal vertebrae, numerous
pits present on the surfaces of the centra and, a foramen present between
the basal part of the fused neural spines, which is similar to that of
*Struthio camelus*. The discoveries of pygostyles from the therizinosauroids
and oviraptorosaurs may provide strong evidence for supporting the origin of
birds from small theropod dinosaurs. The structure of the pygostyle in
specimen V11309 is different from those of *Beipiaosaurus*
(Therizinosauroid) and *Nomingia* (oviraptorosaur). The most parsimonious
interpretation is that these pygostyle-like structures are independently
acquired by *Beipiaosaurus* and *Nomingia* during their evolutionary
Looks like no new taxon named this time, but I cannot be sure having seen
only the abstract.