Yunnanosaurus
Name:
Yunnanosaurus
(Yunnan Province).
Phonetic: Yun-nan-o-sore-us.
Named By: C. C. Young (Yang Zhongjian) -
1942.
Synonyms: Yunnanosaurus robustus.
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Sauropodomorpha.
Species: Y. huangi (type),
Y. youngi.
Diet: Herbivore.
Size: Yunnanosaurus huangi
estimated at about 7
meters long, Yunnanosaurus youngi estimated at
about 13 meters
long.
Known locations: China, Yunnan Province -
Lufeng Formation. Y. huangi is known from the
Zhangjiawa
Member, while Y. youngi is known from the
Shawan Member.
Time period: Y. huangi is
known from the
Hettangian/Sinemurian of the Jurassic, while Y. youngi
is
Aalenian/Bajocian of the Jurassic.
Fossil representation: Y. huangi
known from two
skulls and the post cranial skeletal remains of over twenty
individuals. Y. youngi. Known from a partial
post cranial
skeleton.
Yunnanosaurus
is one of the best represented sauropodomorph
(previously known as
prosauropods) dinosaurs not only in China, but the entire world,
with the fossils remains of over twenty individual Yunnanosaurus
so
far known. This has allowed palaeontologists to become familiar with
most aspects of this genus including the realisation that Yunnanosaurus
would have primarily been quadrupedal whereas the first sauropodomorph
dinosaurs were bipedal, similar to their theropod cousins.
Yunnanosaurus however does not seem to be an
obligate quadruped,
with analysis of the hip, limbs and generally lighter build than
later sauropods, all indicating that Yunnanosaurus
would at the very
least be capable of rearing up on the hind legs.
A
second species of Yunnanosaurus called Y.
robustus is now commonly
thought to represent specimens of the type species Y.
huanghi. This
is because the gracile and robust body morphs while once thought to
represent different species are now thought to represent different
growth stages of the same species, with Y. robustus
the adult form.
In
2007 a new species of Yunnanosaurus was named as
Y. youngi (Lu
et al) from a partial skeleton, however with an estimated length of
about thirteen meters, Y. Youngi was almost
double the size of the
type species Y. huangi. An additional fact
about Y.
youngi is
that it lived much later than Y. huangi during
the early stages of
the mid Jurassic. Not only does this make Y. youngi
one of the last
sauropodomorph dinosaurs to exist, but its later appearance coupled
with the larger size is a clearer indicator of how sauropodomorph
dinosaurs developed into the first true sauropod
dinosaurs which in
turn would develop into one of the largest dinosaur groups.
Possibly
predatory threats to Yunnanosaurus may have
included dilophosaurid
theropod dinosaurs such as Sinosaurus.
Further reading
- Preliminary notes on the Lufeng vertebrate fossils. - Bulletin
of the Geological Society of China 20(3-4):235-239. - C.
C. Young - 1940.
- Yunnanosaurus huangi Young (gen. et sp.
nov.), a new
Prosauropoda from the red beds at Lufeng, Yunnan. - Bulletin of
the Geological Society of China, 22 (1-2): 63-104. - C.
C. Young - 1942.
- The Lufeng saurischian fauna in China. Palaeontologia Sinica,
New Series C 13:1-96. - C. C. Young - 1951.
- New yunnnosaurid dinosaur (Dinosauria, Prosauropoda) From the
Middle Jurassic Zhanghe Formation of Yuanmou, Yunnan province of
China. - Memoir of the Fukui Prefectural Dinosaur Museum 6:1-15.
J. Lu, T. Li, S. Zhong, Y. Azuma, M. Fujita, Z.
Dong & Q. Ji - 2007.
- A new juvenile specimen of Yunnanosaurus robustus
(Dinosauria:
Sauropodomorpha) from Early to Middle Jurassic of Chuxiong
Autonomous Prefecture, Yunnan Province, China. Historical
Biology - Toru Sekiya, Xingsheng
Jin, Wenjie Zheng, Masateru
Shibata & Yoichi Azuma - 2013.
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