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出典:『Wikipedia』 (2011/07/21 15:47 UTC 版)

英語による解説

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Protoavis (meaning "first bird") is a problematic taxon of archosaurian known from fragmentary remains from Late Triassic Norian stage deposits near Post, Texas. Much controversy remains over the animal, and there are many different interpretations of what Protoavis actually is. When it was first described, the fossils were described as being from a primitive bird which, if the identification is valid, would push back avian origins some 60-75 million years. The original describer of Protoavis texensis, Sankar Chatterjee of Texas Tech University, interpreted the type specimen to have come from a single animal, specifically a 35 cm tall bird that lived in what is now Texas, USA, around 210 million years ago. Though it existed far earlier than Archaeopteryx, its skeletal structure is allegedly more bird-like. Protoavis has been reconstructed as a carnivorous bird that had teeth on the tip of its jaws and eyes located at the front of the skull, suggesting a nocturnal or crepuscular lifestyle. Reconstructions usually depict it with feathers, as Chatterjee originally interpreted structures on the arm to be quill knobs, the attachment point for flight feathers found in some modern birds and non-avian dinosaurs. However, re-evaluation of the fossil material by subsequent authors such as Lawrence Witmer have been inconclusive regarding whether or not these structures are actual quill knobs.