Zhenyuanlong (meaning "Zhenyuan's dragon", from Chinese Pinyin 龙/龍 lóng "dragon") 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 (Chinese: 孫氏振元龍). 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 direct evidence of well-developed pennaceous feathers in a large, non-flying dromaeosaur, raising the question of what function such wings would serve.
Discovery The specimen was found by a local farmer near Sihedang in Jianchang, Liaoning Province and was later secured for study at the Jinzhou Paleontological Museum by Zhenyuan Sun, a representative of the museum. There it was further prepared by Zhang Y.-Q. In 2015, the type species Zhenyuanlong suni was named and described by paleontologists Lü Junchang of the Chinese Academy of Geological Sciences in Beijing and Stephen Brusatte of the University of Edinburgh in the United Kingdom. The generic name combines Zhenyuan Sun's given name with the Chinese Pinyin long, meaning "dragon". The specific name refers to his family name. Zhenyuanlong was one of eighteen dinosaur taxa from 2015 to be described in open access or free-to-read journals. The holotype, JPM-0008, was found in the Sihedang locality of Jianchang County of northeastern China's Yixian Formation, which dates from the Aptian age of the Early Cretaceous (125–113 million years ago). The holotype specimen is represented by its sub-adult status, its nearly complete and articulated skeleton lacking only half of the tail, its well preserved skull and lower jaws, and its preservation of vaned feathers on the arms and tail. The fossil is compressed on its stone plate or slab. A counterplate is absent.
Description
Zhenyuanlong suni was a mid-sized dromaeosaurid comparable in length to the similar Tianyuraptor. The fossil skeleton is nearly complete but lacks the last half of the tail, giving the specimen a preserved length of 122.6 centimetres (4.02 ft). Based on comparison to the complete skeleton of Tianyuraptor, it has been estimated that the skeleton of Zhenyuanlong would have been about 165 centimetres (5.41 ft) long when complete. With the added length of long tail feathers, the animal was perhaps up to 2 metres (6.6 ft) in life. The fossil represents a subadult individual, as shown by the fusion of the neural arches having been progressed into the sacrum. Its overall proportions are comparable to Tianyuraptor, a dromaeosaurid from the same formation, and it bears many anatomical similarities to the other Liaoning dromaeosaurids. The skull is well-preserved and similar in shape to that of Tianyuraptor and the related Sinornithosaurus. Its sacrum consists of six vertebrae, four of which are clearly fused, and its tail includes the network of bony support rods typical of dromaeosaurs, as well as middle caudal (tail) vertebrae that are somewhat elongated compared to most other dromaeosaurs. Both pectoral girdles are preserved and the specimen shows non-fused sternal plates. Its leg proportions are similar to other Liaoning dromaeosaurs, with its tibiotarsus longer than the femur at a ratio of around 1.30. This large ratio is typical of Liaoning dromaeosaurs but differs from most other dinosaurs in this group.
Zhenyuanlong had very short arms and the shortest arm-to-leg length ratio of any known dromaeosaurid except for the basal dromaeosaurid Mahakala and the giant unenlagiine Austroraptor. Its arms also exhibit some unique and unusual features seen in few related dinosaurs. The radius of Zhenyuanlong's forearm is among the proportionally thinnest of any theropod dinosaur, comparable only to a handful of basal coelurosaurs and to alvarezsauroids, which had extremely reduced arms and hands. Zhenyuanlong is also unique among Liaoning dromaeosaurids for its second metacarpal being shorter than the combined lengths of the first metacarpal and first bone of the innermost finger.
Feathers 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.
… excerpt ends here. Continue reading the full article.
