Sinosauropteryx
Name:
Sinosauropteryx
(Chines lizard wing).
Phonetic: Sigh-no-sore-op-eh-ryx.
Named By: Ji, Q. & Ji, S. - 1996.
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Theropoda, Compsognathidae.
Species: S. prima (type).
Diet: Carnivore.
Size: Up to 107 centimetres long.
Known locations: China, Liaoning Province -
Yixian Formation.
Time period: Barremian to Aptian of the Cretaceous.
Fossil representation: Three known specimens. Some
specimens are so well preserved they show internal organs and prey.
Sinosauropteryx was the first confirmed feathered but non-avian dinosaur discovered. What this means is that while Sinosauropteryx had protofeathers, it was still more like theropod dinosaurs than birds. Sinosauropteryx is often described as being very small at sixty-eight centimetres long however this measurement was just for the holotype specimen which was a juvenile. Further specimens show Sinosauropteryx to have attained sizes of just over one meter like some other compsognathids. Much of this length is actually the tail and with sixty-four vertebra it is one of the proportionately longest tails in known dinosaurs.
Sinosauropteryx
is so well preserved that many important internal details can be
observed. One of these is the confirmation that dinosaurs, at least
those like Sinosauropteryx, had two oviducts,
not the one like in
modern birds. This is implied by the preservation of two developed
eggs that are placed side by side in an area where the oviducts would
have been. The eggs themselves are thirty-six by twenty-six
millimetres long and wide, and are something that helped confirm the
theory that eggs once associated with the related Compsognathus
probably did not belong to this dinosaur. This was based upon the
observation that while Compsognathus is of a
similar size to
Sinosauropteryx the eggs in question were only ten
millimetres long,
much smaller than those found in Sinosauropteryx.
The
good preservation of specimens has also revealed what Sinosauropteryx
ate. Prey animals included a combination of small lizards and
mammals, two of have which have been identified as Sinobaatar
and
Zhangheotherium,
the latter of which had a spur that secreted venom
on its foot. Insects may have also formed a part of its diet,
particularly when young.
Sinosauropteryx
is usually referred to as a feathered dinosaur although the
‘feathers’ themselves were more like filamentous hairs rather than
the flight feathers of modern birds. However some have argued against
the presence of feathers, with some suggesting that the area around
the skeleton is actually the remains of collagen fibres that once
supported a sail on top of the animal and below the tail. This was
supposedly an adaptation for swimming. Another argued that the
feather covering was merely a product of the preparation process.
The
overwhelming majority of palaeontologists however agree that
Sinosauropteryx had a covering of primitive
feathers around its
body. One clear observation is that there is a gap between the actual
skeleton and feather covering which increases and decreases between
different areas where you would expect the bones to be nearer the
skin. The hairs also vary randomly in size and are darker on the
edges than in the centre indicating that they were hollow as feathers
are known to be.
Sinosauropteryx
was the first and remains one of the few dinosaurs to have its
patterning revealed. An alternating pattern of light and dark bands
on the tail was first initially taken to have been caused by the
splitting of the slab and counter slab resulting in different amounts
of fossil material being divided between the two halves. However in
2002 Longrich pointed out that the bands were very evenly spaced
between one another and were probably not the product of the splitting
of the slab, but instead represented areas of light and dark
pigmentation. Further study as well as observation of further
Sinosauropteryx fossils which show similar tail
banding has supported
this theory. Zhang Fucheng et al. discovered the presence of
melanosomes, the cells which dictate the colour of feathers,
something that can be observed in the feathers of modern birds. This
revealed that the darker areas of pigment were most probably of a
chestnut brown colouration.
The
main body of Sinosauropteryx also had darker
pigment on top of its
body, and lighter pigment underneath. Altogether the colouration of
Sinosauropteryx seems to have been a defensive
adaptation as even
though it was a predator, Sinosauropteryx was not
the only one, and
certainly not the largest active at the time as evidenced by the
presence of Sinocalliopteryx.
A chestnut brown colouring on top would
have allowed Sinosauropteryx to blend into the
forest floor while the
banding on the tail would have broken up the shape so that it did not
immediately look like a tail to a larger predator.
Another
dinosaur to have its patterning revealed is Sinornithosaurus,
which
is also known from the Yixian Formation.
Further reading
- On discovery of the earliest bird fossil in China (Sinosauropteryx
gen. nov.) and the origin of birds. - Chinese Geology (Beijing: Chinese
Geological Museum) 10 (233): 30–33. - Q. Ji & S. Ji - 1996.
- Implications of soft-tissue preservation in the compsognathid
dinosaur, Sinosauropteryx. - Journal of Vertebrate
Paleontology 7
(supplement to 3): 48A. - N. R. Geist, T. D. Jones & J. A.
Ruben - 1997.
- Advances in Sinosauropteryx research. - Chinese
Geology 7: 30–32. -
Q. Ji & S. Ji - 1997.
- An exceptionally well-preserved theropod dinosaur from the Yixian
Formation of China. - Nature 391 (8): 147–152. - P. Chen, Z. Dong
& S. Zhen - 1998.
- Anatomy of Sinosauropteryx prima from Liaoning,
northeastern China. -
Canadian Journal of Earth Sciences 38 (1): 705–727. - P. J. Currie
& P. -J. Chen - 2001.
- Systematics of Sinosauropteryx. - Journal of
Vertebrate Paleontology
22 (supplement to 3): 80A. - N. Longrich - 2002.
- New material of Sinosauropteryx (Theropoda:
Compsognathidae) from
western Liaoning, China. - Acta Geologica Sinica (English Edition) 81
(2): 177–182. - S. Ji, C. Gao, J. Liu, Q. Meng & Q. Ji - 2007.
- A new Chinese specimen indicates that 'protofeathers' in the Early
Cretaceous theropod dinosaur Sinosauropteryx are
degraded collagen
fibres. - Proceedings of the Royal Society B 274 (1620): 1823–1829. -
T. Lingham-Soliar, A. Feduccia & X. Wang - 2007.
- Fossilized melanosomes and the colour of Cretaceous dinosaurs and
birds. - Nature 463 (7284): 1075–1078. - X. Xu & X. Wang -
2010.
-
Additional information on the primitive contour and wing feathering of
paravian dinosaurs. - Palaeontology. 61 (2): 273–288. - Evan T. Saitta,
Rebecca Gelernte & Jakob Vinther - 2018.
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