當初發表時作者相信單爪龍是種鳥類,證據包含整體輕盈的骨骼、四肢的變形(尤其掌骨與腕骨)。牠很可能並非處於鳥翼類的最基礎位置,而是底下較進階的演化支間鳥類(Metornithes),該分類階層約等於當時認為鳥類與恐龍之間還很模糊的界線上(此時學界尚無「非鳥型恐龍」的概念),這使得單爪龍將作為其他所有鳥類的旁系分支。[3]此舉亦符合葛瑞格利·保羅(英语:Gregory S. Paul)提出的假設,他由前肢推斷單爪龍是種再次失去飛行能力的鳥類。
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^Dinosaurs of the Gobi. Mongolia: BBC Horizon. 1993.
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^Schweitzer, M. H., J. A. Watt, R. Avci, L. Knapp, L. Chiappe, M. Norell & M. Marshall. (1999). "Beta-keratin specific immunological reactivity in feather-like structures of the Cretaceous alvarezsaurid, Shuvuuia deserti." Journal of Experimental Zoology, 285: 146–157.
^Rothschild, B., Tanke, D. H., and Ford, T. L., 2001, Theropod stress fractures and tendon avulsions as a clue to activity: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p. 331–336.
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