Name:
Sinornithosaurus
(Chinese bird lizard).
Phonetic: Sine-or-nith-oh-sore-s.
Named By: Xu, Wang & Wu - 1999.
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Theropoda, Dromaeosauridae, Microraptoria,
Microraptorinae.
Species: S.millenii (type),
S.
haoiana.
Type: Carnivore.
Size: Around 120 centimetres long.
Known locations: China, Liaoning Province -
Yixian Formation.
Time period: Aptian of the Cretaceous.
Fossil representation: 2 specimens, with some
other specimens possibly being examples of the genus.
Sinornithosaurus
was especially well preserved, and not only were the presence of
feathers clearly revealed; they showed indications of having
differing colours for different body areas. The feathers, while not
exactly like those of modern birds, are still more advanced than in
other species, including some of the later dromaeosaurids.
This is
significant as it helps cement the argument that birds evolved from
dinosaurs, but not from the later and larger dromaesarids, which
detractors to the theory say is impossible. Instead it proves that
the transition happened earlier with smaller dinosaurs that possibly
also led arboreal lifestyles.
As
a living creature, Sinornithosaurus probably
hunted around the forest
floor looking for things like small mammals. Very interestingly the
scleral rings indicate a cathermal lifestyle, meaning that
Sinornithosaurus would have been active for small
periods throughout
the day or night. Aside from the usual night or day scenario, this
would be good advantage for a forest hunter as light levels would be
constantly changing as it moved through varying vegetation densities in
the forest.
Sinornithosaurus
once had the suggestion put forward that it had a venomous bite. This
was based on an interpretation of the front teeth being elongated and
grooved to allow poison to run through, with space for poison glands
in the skull. However a subsequent study has cast significant doubts
against this theory on the basis that grooved teeth are known
throughout all theropods, and are not indicative of poison delivery.
The study also explained the elongated teeth simply as regular sized
teeth that had partially fallen out as a result of the skull being
crushed during the preservation process. No evidence was found to
support the presence of poison glands on the basis that all the
internal skull areas were as expected to be, with no special area for
glands.
Further reading
- Cretaceous age for the feathered dinosaurs of Liaoning, China. -
Nature 400:58-61 1 July 1999. - Carl C. Swisher, Yuan-qing Wang,
Xiao-lin Wang, Xing Xu & Yuan Wang - 1999.
- A dromaeosaurid dinosaur with a filamentous integument from the
Yixian Formation of China. - Nature" 401:262-266. - Xing Xu, Xiao-Lin
Wang & Xiao-chun Wu - 1999.
- Branched integumental structures in Sinornithosaurus
and the origin
of feathers. - Nature 410 (6825): 200–204. - X. Xu, Z. Zhou &
R. O. Prum - 2001.
- The distribution of integumentary structures in a feathered dinosaur.
- Nature 410(6832) 1084-1087. - Q. Ji, M. A. Norell, K. Q. Gao, S. -A.
Ji & D. Ren - 2001.
- Restudy on a small dromaeosaurid dinosaur with feathers over its
entire body. - Earth Science Frontiers 9 (3): 57–63. - Q. Ji, S. -A.
Ji, C. -X. Yuan, X. -X. Ji - 2002.
- A new species of dromaeosaurids from the Yixian Formation of western
Liaoning. - Geological Bulletin of China. 23 (8): 778–783. - J. Liu, S.
Ji, F. Tang & C. Gao - 2004.
- The birdlike raptor Sinornithosaurus was
venomous. - Proceedings of
the National Academy of Sciences. - E. Gong, L. D. Martin, D. E.
Burnham & A. R. Falk - 2009.
- Evidence for a venomous Sinornithosaurus. -
Pal�ontologische
Zeitschrift - E. Gong, L. D. Martin, D. A. Burnham, A. R. Falk - 2010.
- A reassessment of the purported venom delivery system of the
bird-like raptor Sinornithosaurus. -
Pal�ontologische Zeitschrift - F.
A. Gianechini, F. L. Agnolin & M. D. Ezcurra - 2010.
- Fossilized melanosomes and the colour of Cretaceous dinosaurs and
birds - Nature 463(7284), p. 1075. - Funcheng Zhang, Stuart L. Kearns,
Patrick J. Orr, Michael J. Benton, Zhonge Zhou, Diane Johnson, Xing Xu
& Xiaolin Wang - 2010.