[D] Eshanosaurus deguchiianus [sG] [T]
Xu, Zhao & Clark, 2001
Jurassic Early Hettangian
Saurischia Theropoda Tetanurae Coelurosauria Therizinosauroidea
Dull Purplish Beds, Lower Lufeng Formation, Yunnan, China
Genus - Typespecies
Named for a mandible from Eshan County, Yunnan, where the specimen was discovered (lower part of Lower Lufeng Formation, Hettangian, Early Jurassic).
A substantial phyletic analysis demonstrates the therizinosauroid nature of the mandible versus prosauropods and basal ornithischians, leaving practically no doubt of its systematic position.
IVPP V11579, incomplete left mandibilar ramus with teeth.
Diagnosis (as for the type species)
Small therizinosaurid distinguished by round fenestra in caudal portion of dentary, tooth denticles smaller relative to those in other therizinosauroids; tooth denticles nearly perpendicular to mesial and distal mergins of crown (Xu, Zhao and Clark, 2001)
Xu, Xing, Zhao, Xijin & Clark (2001) \\\"A new therizinosaur from the Lower Jurassic Lower Lufeng Formation of Yunnan, China,\\\" Journal of Vertebrate Paleontology 21(3): 477–483
A specimen collected from the Lower Jurassic Lower Lufeng Formation of Yunnan, China. represents a new genus and species of therizinosauroid theropod. It comprises an incomplete left mandibular ramus and is here named Eshanosaurus deguchiianus.
Distinctive characteristics of the new species include the presence of a round fenestra in the posterior portion of the dentary, small size of tooth denticles, and denticles almost perpendicular to the anterior and posterior edges of tooth crowns.
The discovery of Eshanosaurus deguchiianus extends the record of therizinosauroids from the Early Cretaceous back to the Early Jurassic. Recent phylogenetic hypotheses placing therizinosauroids within Coelurosauria imply this is the oldest known coelurosaur, and that diversification of the group began much earlier than was previously indicated by the fossil record.