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,‭ ‬Xu,‭ ‬Zhao‭ & ‬Clark.
- The affinities of the enigmatic dinosaur Eshanosaurus deguchiianus from the Early Jurassic of Yunnan Province,‭ ‬People's Republic of China,‭ ‬P.M.‭ ‬Barrett [here]
- First definitive therizinosaurid‭ (‬Dinosauria:‭ ‬Theropoda‭) ‬from North America,‭ ‬Kirkland‭ & ‬Wolfe [here] & [here]







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