THE AFFINITIES OF THE ENIGMATIC DINOSAUR ESHANOSAURUS DEGUCHIIANUS FROM THE EARLY JURASSIC OF YUNNAN PROVINCE, PEOPLE'S REPUBLIC OF CHINA
THE AFFINITIES OF THE ENIGMATIC DINOSAUR ESHANOSAURUS DEGUCHIIANUS FROM THE EARLY JURASSIC OF YUNNAN PROVINCE, PEOPLE'S REPUBLIC OF CHINA
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DOI：
10.1111/j.1475-4983.2009.00887.x
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发表时间：
2009-07-01
期刊：
影响因子：
2.6
通讯作者：
Barrett, Paul M.
中科院分区：
文献类型：
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作者：
Barrett, Paul M.
Eshanosaurus deguchiianus是基于中国云南省下侏罗统禄丰组的一个单一的左齿。它最初被认为是兽脚亚目（Theropoda：Coelurosauria）中已知最早的成员，这一结论导致了这个分支（> 6500万年）和许多其他主要谱系在Coelurosauria中的范围显著向下延伸。然而，这一解释受到质疑，一些作者提出，用于将峨山龙归类为Therizinosauroidea的解剖特征更符合基底蜥脚类恐龙的属性。对正模标本的详细研究表明，牙列和齿系的几个特征将埃山龙排除在蜥脚形目之外，并支持它被纳入Therizinosauroidea。如果被认为是早侏罗世的腔上龙，那么峨山龙对于理解早期兽脚亚目恐龙多样化的时间和克里思有重要的意义。此外，它的来源也表明，相当大一部分的腔上龙化石记录可能是失踪或未采样。然而，如果这个分类群要完全纳入更广泛的进化研究，则需要确认埃尚龙的早侏罗纪时代。
Eshanosaurus deguchiianus is based on a single left dentary from the Lower Lufeng Formation (Lower Jurassic) of Yunnan Province, China. It was originally identified as the earliest known member of Therizinosauroidea (Theropoda: Coelurosauria), a conclusion that results in a significant downward range extension for this clade (> 65 million years) and for many other major lineages within Coelurosauria. However, this interpretation has been questioned and several authors have proposed that the anatomical features used to refer Eshanosaurus to Therizinosauroidea are more consistent with attribution to a basal sauropodomorph dinosaur. Detailed consideration of the holotype specimen suggests that several features of the dentary and dentition exclude Eshanosaurus from Sauropodomorpha and support its inclusion within Therizinosauroidea. If accepted as an Early Jurassic coelurosaur, Eshanosaurus has important implications for understanding the timing and tempo of early theropod diversification. Moreover, its provenance also suggests that substantial portions of the coelurosaur fossil record may be missing or unsampled. However, the Early Jurassic age of Eshanosaurus requires confirmation if this taxon is to be fully incorporated into broader evolutionary studies.