Sinosaurus
Name:
Sinosaurus
(Chinese lizard).
Phonetic: Sy-noe-sore-us.
Named By: Young - 1948.
Synonyms: Dilophosaurus sinensis.
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Theropoda, Dilophosauridae.
Species: S. triassicus
(type).
Diet: Carnivore.
Size: About 5.6 meters long.
Known locations: China.
Time period: Sinemurian of the Jurassic.
Fossil representation: Remains of several
individuals from partial remains to almost complete.
The
history of Sinosaurus as a dinosaur taxon goes all
the way back to
1948 when the genus was first formally described. However this
description was based upon very partial remains something that meant
the genus fell by the wayside in popularity stakes, with some
palaeontologists even treating the Sinosaurus
genus as a Nomen
dubium. Then in 1987 new dinosaur fossils were named as
Dilophosaurus sinensis, an Asian species
counterpart to the North
American Dilophosaurus wetherilli. A second and
more complete
individual was attributed to Dilophosaurus sinensis
in 1994. Then
in 2003, the eminent Chinese palaeontologist Dong Zhiming was
studying the original Sinosaurus fossils when he
came to the conclusion
that fossils named as Dilophosaurus sinensis were
actually the same
species of dinosaur as Sinosaurus. Under
international rules
governing the naming of animals, the older name takes priority in
such a situation, so fossil material once labelled as Dilophosaurus
sinensis was now known as Sinosaurus. Dilophosaurus
is still a valid
genus, but at the time of writing it is only the type species,
Dilophosaurus wetherilli, from North America
remains valid.
As
a living dinosaur Sinosaurus would have been a
medium sized theropod
dinosaur that still bore a striking superficial resemblance to the
North American Dilophosaurus; Sinosaurus
even had double head crests
similar to those of Dilophosaurus. These crests
are too fragile to
have been used as weapons, and were almost certainly there for a
primarily display purpose. Sinosaurus also had a
distinct notch
between the pre-maxilla and maxilla (the tooth bearing bones of the
upper jaw), another feature that Sinosaurus
shares with
Dilophosaurus. Despite this similarity, Sinosaurus
is actually
perceived to be more closely related to Cryolophosaurus
from
Antarctica. All together Sinosaurus is believed
to have been a
predatory of other moderately sized dinosaurs such as sauropodomorphs.
Due
to its similarity to Dilophosaurus, Sinosaurus
is usually credited as
being a dilophosaurid
theropod, and since the addition of former
Dilophosaurus sinensis fossils to the genus, more
fossils have now
been added to Sinosaurus. Sinosaurus
was also the first dilophosaurid
theropod to have an almost complete brain case attributed to it, and
at the time of writing Sinosaurus still has the
most complete brain
case. There is currently also speculation that that new fossils of
Sinosaurus described in 2012 are actually of a
second species.
Another
first for this genus is that Sinosaurus is the
first theropod dinosaur
that is known to have developed a dental problem. A 2013 study by
Xing et al covers a tooth socket (ZLJT01) where the dental alveolus
had become lost. The dental alveolus is essentially the part that
forms new teeth (dinosaurs and other toothed archosaurs constantly
grow and replace their teeth, an explanation can be seen on the
Tyrannosaurus
page), and without this no new teeth could grow out
of this socket. It may be that the dental alveolus may have been
wrenched out with the tooth during a fight, but the significant thing
about the find is that after the tooth and dental alveolus were
removed, the jaw healed, though the dental alveolus could never
grow back. This means that in the later stages of this individual’s
life, it would have been walking around with a missing tooth.
The
name Sinosaurus translates to English as ‘Chinese
lizard’, while
the type species name triassicus is a reference to the idea that
Sinosaurus was once believed to have lived in the
Triassic period,
though we now know that Sinosaurus actually lived
in the early
Jurassic. Sinosaurus should not be confused with
the similarly named
Siamosaurus,
or the similarly spelled Spinosaurus.
Further reading
- On two new saurischians from Lufeng, Yunnan. - Bulletin of
the Geological Society of China (Acta Geologica Sinca) 28
(1–2): 75–90. - C. C. Young - 1948.
- Contribution of New Dinosaur Materials from China to
Dinosaurology. - Memoir of the Fukui Prefectural Dinosaur Museum
(Beijing: Fukui Prefectural Dinosaur Museum) 2: 123–131. -
Z. M. Dong - 2003.
- Sinosaurus from Southwestern China. -
Department of Biological
Sciences, University of Alberta (Edmonton): 1–286. - L.
D. Xing - 2012.
- Tooth loss and alveolar remodeling in Sinosaurus
triassicus
(Dinosauria: Theropoda) from the Lower Jurassic strata of the
Lufeng Basin, China". Chinese Science Bulletin
(Springer-Verlag) 58 (16): 1931–1935. - L. D. Xing,
P. R. Bell, B. M. Rothschild, H. Ran, J. P.
Zhang, Z. M. Dong, W. Zhang & P. J. Currie
-
2013.
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