Journal of Ornithology
October 2014, Volume 155, Issue 4, pp 841-851
First online: 09 July 2014
Jurassic archosaur is a non-dinosaurian bird
Stephen A. Czerkas, Alan Feduccia
Abstract
Re-examination utilizing Keyence 3D digital microscopy and low angled illumination of the fossil Scansoriopteryx, a problematic sparrow-size pre-Archaeopteryx specimen from the Jurassic Daohugou Biotas, provides new evidence which challenges the widely accepted hypothesis that birds are derived from dinosaurs in which avian flight originated from cursorial forms. Contrary to previous interpretations in which Scansoriopteryx was considered to be a coelurosaurian theropod dinosaur, the absence of fundamental dinosaurian characteristics demonstrates that it was not derived from a dinosaurian ancestry and should not be considered as a theropod dinosaur. Furthermore, the combination in which highly plesiomorphic non-dinosaurian traits are retained along with highly derived features, yet only the beginnings of salient birdlike characteristics, indicates that the basal origins of Aves stemmed from outside the Dinosauria and further back to basal archosaurs. Impressions of primitive elongate feathers on the forelimbs and hindlimbs suggest that Scansoriopteryx represents a basal form of “tetrapteryx” in which incipient aerodynamics involving parachuting or gliding was possible. Along with unique adaptations for an arboreal lifestyle, Scansoriopteryx fulfills predictions from the early twentieth century that the ancestors of birds did not evolve from dinosaurs, and instead were derived from earlier arboreal archosaurs which originated flight according to the traditional trees-down scenario.
Keywords
Scansoriopteryx Epidendrosaurus Theropod Archosaur Daohugou Biota Jurassic
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