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Yixianosaurus
''Yixianosaurus'' (meaning "Yixian lizard") is a maniraptoran theropod dinosaur genus from the Early Cretaceous of China.
The type species, ''Yixianosaurus longimanus'', was formally named and described by Xu Xing and Wang Xiaolin in 2003. Its partial skeleton was discovered in 2001, in Liaoning at Wangjiagou in northeastern China. The generic name refers to the Yixian Formation. The specific name means "with a long hand" from Latin ''longus'', "long", and ''manus'', "hand".〔Xu, X. and Wang, X. (2003). "A new maniraptoran from the Early Cretaceous Yixian Formation of western Liaoning". ''Vertebrata PalAsiatica'', 41(3): 195–202.〕
''Yixianosaurus'' is known only from a single specimen, holotype IVPP V12638, which likely derived from the Dawangzhangzi Bed (early Aptian stage, 122 million years ago).〔Xu, X. and Norell, M.A. (2006). "Non-Avian dinosaur fossils from the Lower Cretaceous Jehol Group of western Liaoning, China."''Geological Journal'', 41: 419–437.〕 It is a compression fossil, preserved on a single slab, that however has been sawed into several pieces. It consists of the shoulder girdle together with a pair of fossilized arms complete with fossilized feathers and some ribs and gastralia. ''Yixianosaurus'' has a very long hand, 140% of the length of the long humerus. The second finger is the longest. The fingers bear large and recurved claws. The feathers are not preserved well enough to show a specific structure, but they appear similar to the contour feathers of some Yixian Formation birds.〔 The large hands could have served in catching prey or assisted climbing. The total body length has been estimated at 1 metre (3.3 ft), the weight at 1 kilogram (2.2 lbs).〔Paul, G.S., 2010, ''The Princeton Field Guide to Dinosaurs'', Princeton University Press p. 125〕
==Classification==
The describers considered the exact placement of ''Yixianosaurus'' within Maniraptora to be uncertain, but because the hand length resembled that of another feathered dinosaur, ''Epidendrosaurus'' (now ''Scansoriopteryx''), they suggested it was a close relative of the Scansoriopterygidae. Other researchers have suggested the specimen may have come from a dromaeosaurid. Subsequent analyses were divided on whether is it is more primitive and outside the clade Eumaniraptora &ndahs; this would mean that advanced characteristics such as the long hands and short arms evolved independently in this species〔Dececchi, T.A., Hone, D., Larsson, H., Sullivan, C. and Xu, X. (2010). "A re-analysis of the "coeluriasaurian pit-bull" ''Yixianosaurus longimanus'' with implications for the theropod dinosaur diversity of the Jehol Biota." ''Journal of Vertebrate Paleontology'', 28(3): 81A.〕 – or a basal member of the more advanced Paraves. Xu et al. (2013) concluded that the presence of large pennaceous feathers on parts of the forelimb strongly supports that ''Yixianosaurus'' was adapted for limited aerial locomotion.〔Xu Xing, Corwin Sullivan & Wang Shuo (2013) The systematic position of the enigmatic theropod dinosaur Yixianosaurus longimanus. Vertebrata PalAsiatica 51(3): 169-183〕
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