Prints left by a squatting bipedal dinosaur show clearly that the hands faced inwards, as birds' limbs do now to allow for wing folding. The prints, which are almost 200 million years old, are preserved in Utah sandstone.
The dinosaur was a theropod — one of a group of mainly carnivorous dinosaurs, such as tyrannosaurs and velociraptors, that were the ancestors of modern birds. The prints suggest that theropods exhibited bird-like anatomy and resting postures much earlier than previously recognized.
Andrew Milner, curator at Utah's St George Dinosaur Discovery Site, and his colleagues theorize that the unknown creature's hand orientation was for grabbing or holding prey.
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Palaeontology: Bird in the hand. Nature 458, 129 (2009). https://doi.org/10.1038/458129a
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DOI: https://doi.org/10.1038/458129a
