Author: Liao Junqi
Edit: Yuki
Nowadays, more and more fossil evidence proves that birds are descendants of dinosaurs, and "dinosaurs are not yet extinct", "dinosaurs can fly", "dinosaurs have feathers" and so on are not big news.
A series of fossil discoveries of feathered dinosaurs have made the origin of bird flight increasingly clear. Image credit: newscientist | Davide Bonnadonna
However, the path of life evolution is often complicated, and there are always some members of the dinosaur family who like to "go the ordinary way" and find another way to realize their "flying dreams" and bring new surprises to people.
Recently, a team from the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences found a fossil specimen of a small dinosaur that does not play by the rules, Ambopteryx longibrachium, in Liaoning Province. It is not only covered with feathers, but also has a wing membrane like bat wings, just like the "Batman" in the dinosaur world, which is incredible.
A long-armed HunYuan dragon covered with feathers and "bat wings" (restored picture). Image source: References[1]
This ingenious idea of flying is undoubtedly a clear stream of the dinosaur family, and its related research was published as a cover article in the journal Nature today (May 9, 2019).
A strangely shaped family of climbing birds and dragons
The long-armed Hunyuan dragon belongs to the Scansoriopterygidae , a theropod dinosaur that lived in the middle to late Jurassic period, and although only three genera have been found so far and most of them are petite, each with a unique skill and a strange appearance.
For example, Epidendrosaurus ningchengensis was the first dinosaur with distinct arboreal features found so far, with its outermost fingers particularly long, just like today's toe monkeys.[2]
The Ningcheng Tree Dragon has exceptionally slender fingers. Image source: Wikimedia Commons | Qilong
Another example is the Epidexipteryx hui, which holds the record for the earliest use of feathers to show off.
Yao Long: Are the four big feathers on my ass sexy? Image source: Wikimedia Commons
Then there's the famous Yi qi, named for its strange wings, which appeared in nature magazine in 2015. [4] The dinosaur had elongated fingers and wing membranes, and also grew a particularly long rod-like bone to help prop up the wing membranes.
It was the first dinosaur with a wing membrane tissue that was found, but because there was only one fossil, it was poorly preserved, and the wing membrane and rod-like bone had not been found in any other dinosaur relative. Therefore, there is still a lot of controversy about whether this dinosaur really had magical wings that could glide in the sky.
Fossil specimens of Chiptera, from which researchers found rod-like bone and wing membrane tissue. Image source: References[4]
This time, the presence of the new member of the family, the long-armed Hun Yuanlong, provided researchers with a wealth of skeletal and physical information. It put an end to previous controversies and added a touch of fog to the evolution of the origins of bird flight.
Long-armed Hun Yuan Dragon - like a dragon like a bird like a bat?
The fossil specimen of Long-armed Hun Yuanlong was found in the late Jurassic formation of Liaoning Province (about 163 million years ago), and is the most complete fossil of the "Climbing Bird" family found so far, and researchers can even see that it has no digestive tract food in its stomach and infer that it is an omnivorous dinosaur.
A fossil specimen of Long-armed Hun yuan dragon, the dark gray area in the right picture represents the wing membrane, the se on the left side is a special rod-like bone, and the blue area is the undigested stomach contents. Image source: References[1]
Through careful analysis of the fossils, the researchers collected many "strange" features from the long-armed Hun Yuan. It has dinosaur ancestry, but has a miniature tail like a bird, and wings with wing membranes like pterosaurs and bats. It almost became a "hybrid dragon" that integrates several creatures (which is why it is called "Hun Yuan").
The long-armed Hun Yuan dragon was petite, with a body length of only 32 cm and a weight of only about 306 grams, which was smaller than today's pigeons. Most of the dinosaurs we remember have long tails, but their tails are very short, just like today's birds. This shortened tail helps it to keep its center of gravity forward as it flies, thus maintaining balance.
Restoration of the long-armed Hun Yuan Dragon. Image source: Wang Min
The most eye-catching thing is the wings of the long-armed Hun Yuan Dragon. Researchers have found similar wing membranes and unique rod-like long bones to those of " Qi Pterosaurus " on the fossils of " Qiyuan " , a discovery that has made the controversial "odd wing" of " qi pterosaur no longer confusing, and also proved that this dinosaur did use elongated fingers to support the wing membrane to fly. In this way, they can use bats or pterosaurs to fly to conquer the blue sky.
In addition, the long arm of the long-armed Hun Yuan Dragon is not a waste of time. Its forelimbs were unusually long (longer than the length of its hind limbs), not to mention the small short hands of the Tyrannosaurus rex, and even the proportion of the wings of many birds in the Mesozoic Era was not as good as its [5], which can be described as a veritable "long-armed" dragon.
How does such a long arm differ from other flying birds? And how do you help it soar into the sky? Using evolutionary patterns and statistical analysis, the researchers analyzed the particular evolutionary trends of this taxon.
The same as flying but each has its own "long"
For dinosaurs, if you want to fly, the wings are of course an indispensable "hardware", and a long enough forearm becomes the primary condition. Theoretically, the longer the forearm, the wider the wingspan, meaning more power can be provided. The trend toward arm elongation began with the evolutionary branch of paraves in the plesiosaurs.
Near birds, as the name suggests, are closer to the group of birds, including climbing birds and birds (birds with birds wings including chiosaurs, wounded toothed dragons, birds, etc.).
An evolutionary branch of paraves in the plesiosaurs. Image source: References[1]
The claws of this type of dinosaur are very slender, and they have chosen different strategies in the process of exploring flight, embarking on two obviously different paths of flight evolution.
Birds, the representative of bird wings, use the elongated palm (metacarpal bone) with feathers to achieve flight. It's like raising your little hand and slapping your wrist to make a "excitement to take off" gesture. Birds' lightweight and asymmetrical feathers control aerodynamics, while longer palms also provide more adhesion area for the feathers.
Archaeopteryx specimens, can be seen as the metacarpal bone is relatively long. Image source: Wikimedia Commons
The strategy of the ornithischians is to lengthen the arms (humerus and ulna) with wing membranes. It's as if you're pretending to be a vampire, clutching a loose cape with both hands and dancing your teeth and claws to take off. In this case, the longer the arm, the wider and larger the cape, and when it is waved, it can hold up more air to make itself go down the river, and the elongated fingers are also for this effect. As for the extra rod-like bone, it was to stabilize the cape and not let it be overturned when it was in the air. Therefore, the flight mode of long arms and wing membranes was created.
The slender arm bones and phalanges of the long-armed HunYuan dragon, as well as the strange rod-like bones used to stabilize the wing membrane (pointed by the arrow). Image source: References[1]
It is difficult to determine whether these two flight methods are superior or inferior, but it is certain that this bat-like flight of the ornithischians is only a short attempt. Judging from the current fossil record, this pattern appeared only briefly in the middle to late Jurassic period, and disappeared by the Cretaceous.
The bird's flight feather pattern continued from the late Jurassic to the Cretaceous, even escaping the catastrophe that destroyed other dinosaurs, and is the most abundant quadruped today, with more than 10,000 species hovering in the sky around the world, becoming a real "sky overlord".
Birds become today's "sky overlords". Image source: Pixabay
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bibliography
1. Min Wang, Jingmai K. O’Connor, Xing Xu, and Zhonghe Zhou, (2019). A new Jurassic scansoriopterygid and the loss of membranous wings in theropod dinosaurs. Nature.
2. Zhang, F., Zhou, Z., Xu, X. & Wang, X. A juvenile coelurosaurian theropod from China indicates arboreal habits. Naturwissenschaften. 2002, 89: 394–398.
3.Czerkas, S.A., and Yuan, C. (2002). "An arboreal maniraptoran from northeast China." Pp. 63-95 in Czerkas, S.J. (Ed.), Feathered Dinosaurs and the Origin of Flight. The Dinosaur Museum Journal 1. The Dinosaur Museum, Blanding, U.S.A.
4.Zhang, F., Zhou, Z., Xu, X., Wang, X. and Sullivan, C. (2008). "A bizarre Jurassic maniraptoran from China with elongate ribbon-like feathers", Supplementary Informtion. Nature, 455: 46pp.
5.Xu, X., Zheng, X., Sullivan, C., et al., (2015). A bizarre Jurassic maniraptoran theropod with preserved evidence of membranous wings. Nature, 521 (7550): 70–73