page_title: Zhenyuanlong
section_title: Feathers
hierarchical_section_title: Zhenyuanlong / Description / Feathers
caption_attribution_description: English: The holotype of the large-bodied, short-armed Liaoning dromaeosaurid Zhenyuanlong suni gen et. sp. nov. (JPM-0008). From: "A large, short-armed, winged dromaeosaurid (Dinosauria: Theropoda) from the Early Cretaceous of China and its implications for feather evolution." By Junchang Lü &amp; Stephen L. Brusatte
context_page_description: Zhenyuanlong is a genus of dromaeosaurid dinosaur from the Yixian Formation of Liaoning, China. It lived during the Aptian age of the early Cretaceous period, approximately 125 million years ago. It is known from a single specimen belonging to the species Zhenyuanlong suni. This type specimen preserved a nearly complete skeleton that contains traces of feathers, including long tail feathers and large wings. In addition to further complicating diversity of Liaoning dromaeosaurids, this specimen provides the first evidence of well-developed pennaceous feathers in a large, non-flying dromaeosaur, raising the question of what function such wings would serve.
context_section_description: The type fossil of Zhenyuanlong preserves integument on several parts of the specimen, including a "hairy" coat of simple filaments over most of the body and large, vaned feathers on the tail and arms, which would have given the animal a life appearance indistinguishable from a bird. The body feathers of Zhenyuanlong are represented by small regions of imprints in the front and back of the neck. While poorly preserved, these feathers appear to contain small, simple filaments less than a millimeter thick and up to 30 millimeters long. Whether the animal's body feathers were simple and non-shafted or more complex filaments attaching to a central vane is impossible to determine from this specimen.
  Despite its small arms, the feathers that made up the wings were very long, more than twice the length of the humerus (upper arm). The wings were broad, with a total surface area of about one square meter each, but their precise shape is unknown due to taphonomic distortion. The specimen's right wing shows an overlapping complex of primary feathers (which attach to the second digit of the hand), secondary feathers (which attach to the forearm), and coverts (which cover both sets). The overall feather architecture of the wings is similar to that of Microraptor, Changyuraptor, Anchiornis, Eosinopteryx, and basal avialans like Archaeopteryx, but the coverts are noteworthy for being more similar in size and shape to these feathers in modern birds. These are preserved as a row of approximately 30 feathers of a consistent small size that attach perpendicularly to the ulna and third metacarpal of the specimen. The coverts of Archaeopteryx and other basal paravians that preserve them are, by contrast, considerably longer and cover much of the wing.
  The specimen's better-preserved right wing shows that the primary feathers were longer than its secondaries, and the authors estimate approximately 10 primaries and 20 secondaries. An asymmetric shape, as in modern birds, may be visible on some of both primaries and secondaries, but preservational distortion makes it difficult to assess this for certain. Overall, the shape and feather architecture of Zhenyuanlong's wings were most similar to those of Microraptor, though the former lacks any sign of the alula feathers which attach to the first finger in modern birds and possibly Microraptor. 
  Long vaned feathers were also present along the length of the tail, and are preserved as a series of long projections of vanes at a 45-degree angle from the tail vertebrae. While preservation makes symmetry difficult to assess, these feathers appear generally similar to the tail feathers of other birdlike dinosaurs that preserve this region, including Sinornithosaurus, Jinfengopteryx, Anchiornis, Eosinopteryx, and Archaeopteryx. This differentiates the tail of Zhenyuanlong from Microraptor and the related Changyuraptor, which had shorter feathers along the base and middle of the tail but large, complex fans at the tip. However, since the end of Zhenyuanlong's tail is not preserved, it's impossible to rule out the presence of a fan entirely.
  Given the close affinity of Zhenyuanlong with Microraptor, Changyuraptor and Sinornithosaurus, it is noteworthy that the specimen does not preserve any feathers on the hind limbs. Some of its closest relatives are known for long, voluminous vaned feathers attaching to the ankles and lower legs, and Zhenyuanlong's lack of similar feathers may indicate another unique anatomical feature of this animal among its relatives. However, the specimen's hind limbs belong to a piece of slab that preserves no other feathers on the body, while the other pieces all preserve feathers. Therefore, the lack of leg-feathers on Zhenyuanlong may be an artifact of preservation or preparation and, like the presence of a tail fan, cannot be ruled out with certainty.
caption: Detail of the preserved integument, showing vaned feathers on tail and wings
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