Browsing by Author "Ji, Qiang."
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Item Anatomy and systematics of the Confuciusornithidae (Theropoda, Aves) from the late Mesozoic of northeastern China. Bulletin of the AMNH ; no. 242([New York] : American Museum of Natural History, 1999) Chiappe, Luis M.; Ji, Shu-An.; Ji, Qiang.; Norell, Mark A."The osteology and plumage of Confuciusornis sanctus and Changchengornis hengdaoziensis from the Chaomidianzi Formation (previously referred to as the lower section of the Yixian Formation) of western Liaoning Province (China) are described in detail. Confusiusornis sanctus and Changchengornis hengdaoziensis have toothless, beaked skulls (the tomial crest is straight in the former species and strongly curved in the latter) and retain the dorsal portion of the nasal process of the maxilla. The skull of Confuciusornis sanctus is of typical diapsid plan. It possesses a triradiate postorbital that with the squamosal forms a complete supratemporal arcade. Furthermore, a robust jugal-postorbital contact completely separates the infratemporal fenestra from the orbit. Although the postorbital region is not preserved in Changchengornis hengdaoziensis, it likely resembles that of Confuciusornis sanctus. Both species have abbreviated tails with long pygostyles, not the long, bony tail originally reconstructed in Confuciusornis sanctus. Scapulae and coracoids are fused to form scapulocorcoids. The coracoids are strutlike but much shorter than the scapulae. The furculae are robust and boomerang shaped. The sterna are long and nearly flat. The complete basket of gastralia follows the sternum caudally. The wing elements are short, and proportions among individual bones are primitive in that the hand is longer than either the humerus or the ulna and the ulna is shorter than the humerus. The pelvis is opisthopubic. The postacetabular wing of the ilium is much shorter than the preacetabular wing. Differences in plumage, namely the presence or absence of two very long tail feathers, are observed among several well-preserved specimens of Confuciusornis sanctus. This difference is likely the expression of sexual dimorphism, although other biological attributes known for extant populations (e.g. differential molting, correlation between sexual maturity and ornamental plumage) indicate that alternative explanations may also account for the observed plumage variation among specimens of Confusiusornis sanctus. Given the latest Jurassic-earliest Cretaceous age of the Chaomidianzi Formation, Confusiusornis sanctus and Changchengornis hengdaoziensis are surely among the oldest know birds after the Early Tithonian Archaeopteryx lithographica. Confusiusornis sanctus and Changchengornis hengdaoziensis thus furnish the earliest record of beaked birds. The fully diapsid skull of Confusiusornis sanctus, and presumably of Changchengornis hengdaoziensis, and the absence of a bending zone on the base of the snout suggest that earlier interpretations of the skull of Confusiusornis sanctus as prokinetic are incorrect. Confuciusornis sanctus probably had very limited cranial kinetic capabilities, if any. Optimization of the postorbital-jugal contact, a character intimately correlated with intracranial kinesis, in a phylogeny of basal avians indicates that the essentially akinetic condition of the skull of Confuciusornis sanctus is a reversal derived from forms possessing kinetic properties. Recent recognition of two additional species of Confuciusornis - Confuciusornis chuonzhous and Confuciusornis suniae - are based on anatomical misinterpretations. Thus, Confuciusornis suniae and Confuciusornis chuonzhous are regarded as junior synonyms of Confuciusornis sanctus. Confuciusornis sanctus is the sister-taxon of Changchengornis hengdaoziensis, and both are placed within the Confuciusornithidae. Some of the synapomorphies supporting this grouping include the presence of edentolous jaws, a rostrally forked mandibular symphysis, a reduced claw of manual digit II, and a V-shaped caudal margin of the sternum. The Confuciusornithidae is considered to be the sister-group of a clade composed of the Enantiornithomorpha and the Ornithuromorpha. This phylogenetic interpretation is far more parsimonious than previous systematic hypotheses placing the Confuciusornithidae as either within the Enantiornithes or as its sister-group. Purported climbing specializations of Confuciusornis sanctus are evaluated in light of the available anatomical evidence. We conclude that both Confuciusornis sanctus and Changchengornis hengdaoziensis were ill suited for tree climbing. The foot of Changchengornis hengdaoziensis, however, suggests a greater grasping ability than that of Confuciusornis sanctus. It is argued that both Confuciusornis sanctus and Changchengornis hengdaoziensis were able to fly and take off from the ground. The remarkable concentration of specimens of Confuciusornis sanctus from a relatively small quarry near the village of Sihetun (Liaoning Province) suggests several events of mass mortality and, perhaps, a gregarious behavior"--P. 3.Item An early ostrich dinosaur and implications for ornithomimosaur phylogeny. American Museum novitates ; no. 3420(New York, NY : American Museum of Natural History, 2003) Ji, Qiang.; Norell, Mark.; Makovicky, Peter J.; Gao, Keqin, 1955-; Ji, Shu'an.; Yuan, Chongxi.A new ornithomimosaur from the Yixian Formation of Liaoning Province Peoples Republic of China is described. These beds are near the Jurassic-Cretaceous boundary. This specimen is interesting because it has several primitive characters for ornithomimosaurs such as teeth and a short first metacarpal. This taxon is placed in a phylogenetic analysis of Coelurosauria and shown to be near the base of the ornithomimosaur clade. Using this phylogeny we comment on the biogeographic history of this group.Item Juvenile birds from the early Cretaceous of China : implications for enantiornithine ontogeny ; American Museum novitates, no. 3594(New York, NY : American Museum of Natural History, 2007) Chiappe, Luis M.; Ji, Shu'an.; Ji, Qiang.Mesozoic remains of embryonic and early juvenile birds are rare. To date, a handful of in ovo embryos and early juveniles of enantiornithines from the early Cretaceous of China and Spain and the late Cretaceous of Mongolia and Argentina have comprised the entire published record of perinatal ontogenetic stages of Mesozoic birds. We report on the skeletal morphology of three nearly complete early juvenile avians from the renowned early Cretaceous Yixian Formation of Liaoning Province in northeastern China. Evidence of the immaturity of these specimens is expressed in the intense grooving and pitting of the periosteal surfaces, the disproportionately small size of the sterna, and the relative size of the skull and orbits. Size notwithstanding, anatomical differences between these three specimens are minimal, leaving no basis for discriminating them into separate taxa. Numerous osteological synapomorphies indicate that they are euenantiornithine birds, the most diverse clade of Enantiornithes, but their identification as members of a particular euenantiornithine taxon remains unclear. Their early ontogenetic stage, however, provides important information about the postnatal development of this specious clade of Cretaceous birds. The presence of pennaceous wing feathers suggests that fledging occurred very early in ontogeny, thus supporting a precocial or highly precocial strategy for enantiornithine hatchlings. The morphology of these new early-stage juveniles is also significant in that they allow a better understanding of the homologies of several avian compound bones because the components of these skeletal compounds are preserved prior to their coossification. The general morphology of the wrist and ankle of these juveniles highlights once again the striking similarity between nonavian theropods and early birds.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 Ordosemys (Testudines, Cryptodira) from the Yixian Formation of Liaoning Province, northeastern China : new specimens and systematic revision. American Museum novitates ; no. 3438(New York, NY : American Museum of Natural History, 2004) Tong, Haiyan.; Ji, Shu'an.; Ji, Qiang.; Zhongguo di zhi bo wu guan.The Yixian Formation, in Liaoning Province, northeastern China, has yielded abundant turtle remains which were described previously as Manchurochelys liaoxiensis. Study of a new collection in the Geological Museum of China and reexamination of previously studied IVPP collection allow us to assign this turtle to Ordosemys. Additional primitive features observed in Ordosemys liaoxiensis confirm its basal position among Centrocryptodira.