Ji Qiang & Ji Shuan, Chinese Geology, 1997, 7,
p. 30-32 and cover page 3.
Since the formal description of the Sinosauropteryx prima,
there have been positive valuation on its scientific significance
and hot arguments about its classification. Some dinosaur paleontologists
suggest that the Sinosauropteryx belongs to a dinosaur (Reptilia)
based on its anatomical features of bones. We think that the
fossil, with feathers, should belong to Aves. In December 1996
when the Chinese National Geological Museum celebrated its 80th
anniversary, the Beipiao Municipal Government of Liaoning Province
presented a new piece of Sinosauropteryx specimen to our museum.
Here is a report on our preliminary study on this piece of fossil,
with further discussions on the classification of the Sinosauropteryx.
I. Additional descriptions on the fossil
Family Sinosauropterygidae Ji et Ji, 1996
Genus Sinosauropteryx Ji et Ji, 1996
Sinosauropteryx prima Ji et Ji, 1996
Positive Specimen: a complete impuberism, Specimen number
of China National Geological Museum: GMV2123.
New Specimen: a complete adupt individual, GMV2124.
Location and Strata: Sihe Village, Shangyuan, Beipiao City,
Liaoning. Lower part of Yixian Formation, Upper Jurassic.
Modified Features The eye aperture is large. The upper jaw
bone is well developed, with coarse tooth bones. Teeth on upper
and lower jaws are well developed,. There are about 12 teeth
on each side. The front teeth are cone-shaped. The rear ones
are flatted, with saw-tooth edge on the rear. The tail is very
long, with about 50 candal vertebras. The fore limbs are short.
Its bones are fine (small). The pubis is long and combined at
the end, stretching down forwards. The closer end of ischia is
wide, while the farther end is narrow. The hind limbs are long
and coarse. The tibia is longer than ? Thinning of fibula is
not obvious. mt (? p31 figure 1 mtI - mtV) are coarse and long,
not combined. The first (I) mt is short and small, located at
a higher position. The fifth mt (V) existed. Phalanx is coarse.
Feathers are primitive, with weak evolution. The feather axes
are clear.
Additional Description The Sinosauropteryx on the positive
specimen (GMV2123) is 0.65 m long, representing an immature bird.
Its features are described by Ji Qiang and Ji Shuan (1996). The
new found specimen (GMV2124) measures 1.06 m, representing an
adupt bird (Plate 1, Covering page 3), is further described here.
Skull The right side is preserved. Partial osteosututes are
visible. The skull is flattened due to compression, but overall
shape is good. The skull is 11.3 cm long. The hole before eye
is large, oval-shaped. The eye aperture (orbit) is large and
round, slightly located backward. The front part of jaws is well
developed, the rear part narrow and long. The lacimal bone is
straight up, upper part is wider, it is therefore T-shaped. The
jugal is narrow and long. The parietal bone is large. The quadrate
bone is L-shaped.
The lower jaw is coarse. Its rear part is higher. Tooth bones
are well developed. Upper bone (?) is larger.
Teeth are well grown. There are 11 or 12 teeth on upper jaw,
12 on lower jaw. 4 - 5 teeth in the front jaw and lower jaw are
straight sharp cone-shaped. Their ends sharpen. The diameters
at the base and middle are around 1 mm. Teeth on the upper jaw
and at the rear are short knife shaped. Their base is above 2
mm wide. The longest tooth cap (?) is 5.5 mm high, bending backward.
The rear edges show saw-tooth (Plate 2, covering page 3). The
height of tooth caps on upper jaw decreases from the front to
the back. The last one has a height of only 1 mm or so.
Vertebras and ribs The neck vertebras are not well preserved.
Their number and shape are not clear. But the third or forth
vertebra is 1.5 cm. The front neck ribs(?) are very long, over
2.3 cm.
Only a few back vertebras are preserved, separated and not
connected to each other. At least 12 pair or single back ribs
are visible, coarse, curved. Closer ends are wide and flat, with
2 joints. The longest rib at the front and middle part is 8 cm.
The middle diameter is about 0.2 cm. The ribs at the rear part
are short and straight, only 4 cm long. Abdominal ribs are thin
and weak (fragile).
The tail is long. Candal vertebras are clear. Only 34 of
them are preserved. The total should be over 40. The candal vertebras
at the front part are 1.5 -1.6 cm long, about 0.8 cm high. The
lower edge of vertebras is obviously concave. Protrusioon is
well grown. Transverse process is obvious. The nerve ring is
at the mid-rear part of upper side of vertebras, slightly dipping
backward. The circuls venosus is well grown, 1.1 - 1.3 cm long.
The farther end is a little flat and wide, located between the
lower ends of two neighboring vertebras. The vertebras at middle
part are similar in length (around 1.6 cm) to those at the front
part, but height much less ( 0.6 -0.7 cm). Both protrusion and
cymbocephale are well developed. The protrusion is especially
clear. Its inner side is connected to the outer side of cymbocephale
of the vertebra in front. Nerve rings are low. Circulus venosus
becomes smaller. Its end sharpens, 0.8 - 1 cm, dipping backward.
The candal vertebras at the rear are small. To view from side,
they are rectangle. Their length is twice the height. Both protrusion
and cymbocephale are low but thin and long. The circulus venosus
is thin, right on the bottom of vertebras.
Pectoral girdle and fore limbs Shoulder bones are thin and
long. The mouth bone (?) is roughly irregular fan-shaped. The
closer end of humerus is wider. Finger bones (?) are thin and
long, with large claws. Although the fossil is not preserved
completely, it is clear that fore limbs are very short and small
in contrast to hind limbs.
Girdle and hind limbs This part is preserved completely (Figure
1). The girdle is coarse. Intestinal bone is 9.1 cm long, 2.7
cm high. Its upper edge is convex and arc-shaped, similar to
that of Theropoda. Pubis is very long -- 9.6 cm. Its lower end
is combined and dipped forward. The pubis is slightly shorter
than thigh. Significantly, a 2 cm - long mammalís tooth
bone (?) and teeth are preserved between the two pubises of the
Sinosauropteryx. The ischia is 5.6 cm long, with closer end wider
and farther end narrower. The back of ischia is concave.
The thigh is 10.8 cm long. Two ends are round, wider than
the middle part, slightly curved backward. The tibia is very
long - 15.1 cm. The closer end is 2.2 cm wide, and middle part
becomes narrower. The tibia is straight. The length ratio of
the tibia to the thigh is about 1.4. The fibula is also thin,
closely attached to the tibia. Its closer end is 1.5 cm wide.
Several tarsuses are visible. Tibial or fibular tarsuses
are larger, and lune (half-moon).
mt (fig 1) are long and wide, not combined. II - IV are over
9 cm. The first is very short and small, only 1.6 cm long. Its
upper end is 4 cm higher than II. The fifth (V) exists, small,
at higher location.
Segments of pubises are various in width and length. Pubis
I is small. II is longer and wider. III is the largest. Pubis
pattern (?): 2-3-4-5-0.
Feathers Two feathers are seen under the front candal vertebra
and at the end of the tail. The foliated feather is 2.3 cm long,
1.1 cm wide ,with feather axis (?).
It should be pointed out that a cross section of feather
axes are found. Feather pulps and sheathings are near round or
oval, and distributed in concentric pattern ( Plate 3, Covering
page 3).
Comparison Only two Sinosauropteryx specimens have been described
now. They are both from Sihe Village, Shangyuan, Beipiao. They
have many common or similar features, such as large skull, coarse
lower jaw, sharp teeth, same numbers of back vertebras (ribs),
long tail, short and small fore limbs, coarse hind limbs, not
combined mt, coarse girdle, long and forward-stretching pubis,
as well as existence of feathers. Therefore, both should belong
to the same species. The original specimen is 65 cm. Its feathers
are more primitive, with scale impression under the closer side
of the tail. It represents a immature animal (Ji Qiang and Ji
Shuan, 1996). The adult individual (GMV2124) described here is
106 cm long. The feathers are foliated, with feather axes, which
reveals different grown stages of Sinosauropteryx. We regard
it as the new specimen of the Sinosauropteryx prima, because
its skull, teeth, girdle, hind limbs, and candal vertebras are
better preserved.
In addition to the difference in size, this two specimens
also have some different features (Table 1). However, those differences
are caused by various growth stages and can not be used to classify
into two different species.
Table 1 Comparison of Sinosauropteryx prima Immature and
adult
Features Positive specimen (GMV2123) New Specimen (GMV2124)
Immature Adult
Length 65 cm 106 cm
Hole before eye small Large, short round shape
Thigh length: tibia length 1:1.13 1:1.40
Candal vertebra 54 over 40
Feather short, no differentiation large, foliated, with axes
If the positive (original) specimen is hard to believe to
be a bird, due to its short and not differentiated feathers,
then the large feathers in the new specimen proves that the Sinosauropteryx
is a bird.
II. The classification of Sinosauropteryx
It is no doubt that the bone structure of the Sinosauropteryx
is obviously similar to Theropoda, such as large skull, sharp
teeth, saw-tooth at rear edge of back teeth., strong skeleton,
strong girdle and hind limbs, numerous scandal vertebras, and
so on. However, so typical features of a bird appeared on the
Sinosauropteryx, such as feathers. The transitional feature shows
the close relation between dinosaur and bird, which is invaluable
scientifically. To discuss the Sinosauropteryx belongs to dinosaur
or bird, it is necessary to see the biological standard distinguishing
reptile and bird.
It is well known that modern reptiles with concas are cold-blooded
and birds with feathers are warm-blooded. We believe that the
most significant difference between a reptile and a bird is features.
Feathers are the most important feature of a bird. In fact, the
establishment of such a high classification unit as ìclassî
is based on biological standard, not only on bone structure especially
when we classify some transitional species. The bone structures
of the Germany Archaeopteryx lithographica are also similar to
small Theropoda. But the existence of feathers shows that it
belong to birds. There is no reason to disregard that the Sinosauropteryx,
with feathers, is also a bird.
Birdsí feathers and reptileís imprication are
of the same source. The appearance of feathers, evolved from
imprication, was first to keep the body temperature, further
made flight possible. If the feathered Sinosauropteryx is believed
to belong to dinosaurs,
Then how do we define a bird? What is the boundary between
a bird and a reptile? A bird is the only type of animals with
feathers. Based on that definition, we strongly believe that
the Sinosauropteryx belongs to Aves. The fact that the skeleton
of the Sinosauropteryx looks like a small Theropoda confirms
that birds are evolved from small Theropoda (Ostrom, 1976). Protarchaeopteryx
robusta from higher strata than the Sinosauropteryx is in similar
evolution level to the German Archaeopteryx lithographica (Ji
Qiang and Ji Shuan, 1976). And more advanced Confuciusornis sanctus
and other early birds have also been found (Hou Lianhai and Zhou
Zhonghe, 1995), which represents different stages of early birds.
The Sinosauropteryx is most primitive bird, the real origin of
birds known to date.
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