Long-arm Muddy Yuanlong-- "Chimera", a bird dragon with bat wings

The first person to break this perception was Yi qi, which was published by Professor Xu Xing in 2015. Many parts of the body of the pterosaur are covered with feathers, which is similar to many other feathered dinosaurs. However, the forelimb area of this dinosaur still retains the imprint of the pterygium and has a rod-like long bone. Such long bones have no corresponding homologous structure in other dinosaurs and birds. On the contrary, similar structures can be seen in today's gliders such as hamsters. The main function of this long bone is to support the skin membrane, thus expanding the area of contact with air to increase buoyancy. As a result, the pterosaur was restored to have membranous wings and be able to glide like a pterosaur. Since only one specimen of the pterosaur has been found so far, although it caused a great sensation when it was published, scientists are very controversial about the structure of the rod-shaped long bone and pterygoid membrane.

Fossils of Hun Yuanlong with long arms

The long-arm muddy yuan dragon, together with the strange pterosaur, the ornithosaur, the Ningcheng tree habitat dragon and Hu's Yao dragon, belong to the taxon of the ornithosaurus. The taxonomic name of ornithosaurus was first put forward by scientists who discovered ornithosaurus in 2002. however, since the day it was proposed, its phylogenetic position in theropods has been erratic. At first, it was considered to be a primitive ornithopod, and later it was considered to be the branch of dinosaurs closest to ancient birds, and now most views tend to be that they belong to paranornids. It is slightly farther than the relationship between Dentosaurus and Dentosaurus and ancient birds. It is this slightly distant kinship that has led ornithosaurs to embark on a completely different path of flight evolution.

Unlike most dinosaurs that walk and run on the ground, ornithosaurs are a kind of arboreal dinosaurs and one of the smallest non-avian dinosaurs known. The body length of the juvenile specimen of ornithosaurus is about 16 cm, which is about the size of a sparrow. The body length of an adult Hushi Yaolong, excluding tail feathers, is about 25 cm, which is basically the same as that of a domestic pigeon, and the largest pterosaur is only 380 grams. I have to say that this family is a group of small elves, and it is precisely because of its light size that it is possible to glide in the jungle. Imagine if they are all a group of big guys weighing several tons. Flying gracefully in the air may just be an extravagant hope.

In addition to arboreal life, another significant difference between ornithopods and other theropod dinosaurs is that their third finger, the outermost finger, is much longer than the first and second fingers. of all other known theropods, the second finger is the longest. In the past, some people thought that ornithosaurus used their third finger to hook larvae from wood, just like existing finger monkeys. However, after a comprehensive study of the specimens of the strange pterosaur and the newly discovered Brachiosaurus, the researchers found that the lengthened third finger of the two dinosaurs, together with the "rod bone" extending from the carpal bone, is used to support a bat-like pterygoid for gliding. Because the fingers lack flexible joints, it is actually difficult to hook larvae. However, the pterygoid surfaces of these two dinosaurs only used a lengthened third finger and extra rod-shaped long bones to support the pterygoid, which is very different from the way the bat's pterygoid uses the second to fifth fingers to support the pterygium. It is more similar to the pterosaur's pterosaur supporting the pterygoid membrane with the lengthened fourth finger, but the pterosaur does not have the rod-shaped long bone of this wrist.

Its tail is also different from most other non-ornithopods. Its tail is very short and is a tail Heald bone formed by a series of tail vertebrae. Other non-ornithopods with similar healing tail Heald bones are only some egg-stealing dragons and Therizinosauria. Dinosaurs that are more closely related to birds, such as dinosaurs and toothed dinosaurs, all have a long tail. Such a shortened tailbone can further move the body's center of gravity forward, making the dinosaur more stable when gliding.

The abdomen of the long-armed Hun Yuan dragon fossilized specimen contains a small amount of stomach stone and large fragments of what appear to be bones, which may not be fully digested food. Before the discovery of this specimen, scientists did not know much about the eating habits of ornithosaurs, but the peculiar tooth shape of the dinosaurs and the stomach stones and bone fragments that may be stomach contents found in the specimens of the long-armed turbid dinosaur suggest that ornithosaurs were omnivorous dinosaurs.

All known ornithosaurs lived in the late Jurassic, and similar membranous wings disappeared in later Cretaceous dinosaurs. The wings composed of flying feathers appeared from the late Jurassic to the Cretaceous and finally formed the wings of birds after a long evolution, making birds the most diverse living quadrupeds. The unique wing structure of ornithosaurus may represent a short but unsuccessful attempt in the evolution of bird flight.

Restoration map of Hun Yuanlong with long arms