Eshanosaurus
Name:
Eshanosaurus
(Eshan lizard).
Phonetic: E-shan-o-sore-us.
Named By: Xu, Zhao & Clark - 2001.
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Theropoda, Coelurosauria? Therizinosauria?
Species: E. deguchiianus
(type).
Diet: Uncertain.
Size: Unknown due to lack of remains.
Known locations: China, Yunnan Province -
Lower Lufeng Formation.
Time period: Hettangian of the Jurassic.
Fossil representation: Partial left dentary (lower
jaw) preserved in three parts.
Not
a lot is known about Eshanosaurus, yet it has
still managed to be a
controversial dinosaur. Thought to be one hundred and ninety-six
million years old, the partial dentary of Eshanosaurus
(currently
the only part known) goes as far back as the Hettangian stage of the
Jurassic. The describers of the dentary proposed two things, one,
the dentary may be from the first coelurosaur. Two, aside from
being the first coelurosaur, it may be the first therizinosaur,
speculation based upon traits that match those of the therizinosaurs.
Not
all palaeontologists agree with these ideas however mainly because this
would create a massive gap of tens of millions of years between
Eshanosaurus and the first confirmed therizinosaur
remains that to date
are known from the Early Cretaceous. One notable case is the
description of the first known North American therizinosaur by Kirkland
and Wolfe, where the teeth of Eshanosaurus were
described as having
ridges similar to prosauropods. The describers of Eshanosaurus
however tested for this and found the dentary and teeth to still be
those of a therizinosaur. Support for the original theory also comes
from a 2009 study by Paul Barrett that yielded the same conclusion
that the Eshanosaurus holotype has known
therizinosaur features that
are absent in known prosauropods.
For
the time being Eshanosaurus remains a problematic
genus. But if other
factors to explain the similarity to therizinosaurs such as convergent
evolution can be ruled out, and ideally the discovery of further
remains found that can bridge the gap and complete our understanding of
the coelurosaurs and therizinosaurs, then Eshanosaurus
may yet help
to re-write palaeontology books across the board.
Further reading
- A new therizinosaur from the Lower Jurassic Lower Lufeng Formation of
Yunnan, China. - Journal of Vertebrate Paleontology 21(3):477-483. - X.
Xu, X. Zhao & J. M. Clark - 2001.
- The affinities of the enigmatic dinosaur Eshanosaurus deguchiianus
from the Early Jurassic of Yunnan Province, People's Republic of China.
- Palaeontology. 52 (4): 681−688. - P. M. Barrett - 2009.
Random favourites
 |
 |
 |
 |