It was once thought limited to forms such as Archaeopteryx, but recent discoveries in China have shown that it was widespread in species like Velociraptor.
The examination of the tail of a Psittacosaurus fossil has been used to argue for the presence of this physical feature in Ornithischian dinosaurs, but that view is heterodox. The presence of ulnar papillae is one way of telling if a fossilized animal had this physical feature. Fossil evidence for this physical feature often comes from the Yixian valley. This feature is found only in (*) theropods, the group in which it first evolved. It was once thought limited to forms such as Archaeopteryx, but recent discoveries in China have shown that it was widespread in species like Velociraptor. For ten points, name this skin-covering feature that evolved in dinosaurs and is today found on birds.
The examination of the tail of a Psittacosaurus fossil has been used to argue for the presence of this physical feature in Ornithischian dinosaurs, but that view is heterodox.
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