Browsing by Author "Hwang, Sunny H."
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Item New specimens of Microraptor zhaoianus (Theropoda, Dromaeosauridae) from northeastern China. American Museum novitates ; no. 3381(New York, NY : American Museum of Natural History, 2002) Hwang, Sunny H.; Norell, Mark.; Ji, Qiang.; Gao, Keqin, 1955-New specimens of the diminutive theropod dinosaur Microraptor zhaoianus are described. These specimens preserve significant morphological details that are not present or are poorly preserved in the holotype specimen, including aspects of the manus, pectoral girdle, dorsal vertebrae, ilium, and sacrum. These specimens were coded into a current matrix of theropod morphological characters. Microraptor is found to be the sister taxon to other dromaeosaurs. Dromaeosaurids are monophyletic and together with a monophyletic troodontid group form a monophyletic Deinonychosauria, which is the sister taxon to Avialae. Apparently small size is primitive for Deinonychosauria, which has implications for bird origins.Item A small derived theropod from Öösh, early Cretaceous, Baykhangor Mongolia ; American Museum novitates, no. 3557(New York, NY : American Museum of Natural History, 2007) Turner, Alan H. (Alan Hamilton); Hwang, Sunny H.; Norell, Mark.; Mongolian-American Museum Paleontological Project.; Mongolyn Shinzhlekh Ukhaany Akademi.A new theropod dinosaur, Shanag ashile, from the early Cretaceous Öösh deposits of Mongolia is described here. The new specimen (IGM 100/1119) comprises a well-preserved right maxilla, dentary, and partial splenial. This specimen exhibits a number of derived theropod features, including a triangular anteriorly tapering maxilla, a large antorbital fossa, and maxillary participation in the caudally elongate external nares. These features resemble the early Cretaceous dromaeosaurids Sinornithosaurus millenii and Microraptor zhaoianus, as well as the basal avialan Archaeopteryx lithographica. A comprehensive phylogenetic analysis including 58 theropod taxa unambiguously depicts the new Öösh theropod as a member of Dromaeosauridae. Relative to other dromaeosaurids, Shanag ashile is autapomorphic in its lack of a promaxillary fenestra and in the presence of interalveolar pneumatic cavities. The discovery of IGM 100/1119 expands our knowledge of early Cretaceous dromaeosaurids and the faunal similarity between the Öösh and the Jehol biotas.Item A troodontid dinosaur from Ukhaa Tolgod (late Cretaceous Mongolia). (American Museum novitates, no. 3446)(New York, NY : American Museum of Natural History., 2004) Norell, Mark.; Hwang, Sunny H.; Mongolian-American Museum Paleontological Project.; Mongolyn Shinzhlėkh Ukhaany Akademi.Here we describe a fragmentary troodontid specimen from the sublocality of Grangers Flats at the late Cretaceous locality of Ukhaa Tolgod, Omnogov, Mongolia. This specimen is provisionally referred to the coeval Saurornithoides mongoliensis. IGM 100/1083 displays a pattern of tooth replacement that is like that of basal avialans. The presence of this pattern in avialans has been used by some to refute a theropod origin for this group.