Wednesday, December 09, 2015

Therizinosaurs From Upper Cretaceous Uzbekistan

Therizinosauroidea (Dinosauria: Theropoda) from the Upper Cretaceous of Uzbekistan


Sues et al


Skeletal remains of indeterminate therizinosauroid dinosaurs are present in the Cenomanian Khodzhakul Formation and common in the Turonian Bissekty Formation of Uzbekistan. At least two taxa are present in the Bissekty Formation based on different frontal and humerus morphotypes. Phylogenetic analysis based on a dataset with 348 morphological characters and including all known therizinosaurian taxa places the Bissekty taxa as derived non-therizinosaurid therizinosauroids. The Bissekty therizinosauroids are more derived than Alxasaurus elesitaiensis in the extensive pneumatization of the postcranial axial skeleton, the absence of teeth in the anterior portion of the dentary, the weak development or even absence of pits for the collateral ligaments on the manual phalanges, and the subtriangular medial aspect of the distal end of the humerus, with the entepicondyle positioned well medial to the ulnar condyle. They are less derived than Therizinosauridae in the presence of a basisphenoid recess, the absence of pneumatic openings on the anterior caudal vertebrae, the distal end of metacarpal III not being ginglymoid in dorsal view, and the separation of the femoral head from the neck of that bone by a raised ventral rim.

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