Yi qi
| Yi qi | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Yi qi , graphic reconstruction |
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| Temporal occurrence | ||||||||||||
| Callovium to Oxfordium ( Jura ) | ||||||||||||
| 166.1 to 157.3 million years | ||||||||||||
| Locations | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name of the genus | ||||||||||||
| Yi | ||||||||||||
| Xu et al. , 2015 | ||||||||||||
| Scientific name of the species | ||||||||||||
| Yi qi | ||||||||||||
| Xu et al. , 2015 |
Yi qi (from Chinese 翼 , pinyin yì - "wing" and奇 , qí - "unusual") is the only known species of the monotypical dinosaur genus Yi . It is a species of the pinnate Scansoriopterygidae from the middle or late Jurassic about 160 million years ago, which is so far only known from a fossil from China .
The animal was a small tree-living dinosaur that, like other Scansoriopterygidae, had an elongated third finger on which a gliding-flight skin was stretched. The flight membrane was supported by a bony strut on the wrist , which was previously only found in this species. The appearance of the flying skin probably roughly resembled that of a bat .
features
Yi qi is only known from a single, only partially traditional skeleton. This holotype (STM 31-2) is currently in the collection of the Shandong Tianyu Museum of Nature . The fossil was compressed and is on a stone slab and an imprint. It is anatomically connected, consisting of the skull, the lower jaw, the neck and the extremities, while the spine, the pelvis and the tail are largely absent. Yi qi was a relatively small dinosaur that probably weighed only about 380 grams.
As with other Scansoriopterygidae, the head was short with a rounded snout and a downwardly curved lower jaw. The few teeth that have survived are only in the area of the tip of the snout, the front four teeth on both sides being the largest teeth and pointing slightly forward; the lower front teeth are pointing even more clearly forward. The long and slender forelimbs were essentially those of other dinosaurs of the paraves . As with other Scansoriopterygidae, the first finger is the shortest and the third finger is the longest. In contrast to all known dinosaurs, there is a long spur-like bone on the wrist, which exceeds both the third finger and the ulna in length and is directed backwards. It is slightly curved and becomes narrower towards the end. This stylus represents either a newly formed bone of the wrist or an ossified cartilage rod; it supported the animal's gliding skin as a tensioning element.
The Yi qi fossil shows a clear feathering ; unlike other more highly developed theropods within the Pennaraptora , which usually have highly developed feathers, the feathers were very simple and brush-like and consisted of a spiky shaft with thinner filaments as a flag. Accordingly, the structures were comparatively hard and stiff. The feathers covered most of the body starting from the snout area. The head and neck feathers were long and formed a dense coat, the body feathers were even longer and denser, making their exact structure on the fossil difficult to see. The longest feathers with a length of about six centimeters were located on the forearm and the bone spur and the metatarsus was also feathered.
There were also small pieces of wrinkled skin between the fingers and the bone spur, which suggest that Yi qi, unlike all other known dinosaurs, had a skin made of skin instead of an arm or wing covered with feathers. The flight membrane stretched between the shorter fingers and the elongated third finger, the additional bone spur and possibly also to the body, although this part has not survived in the only known fossil. Due to the flight membrane, the animal probably had an appearance similar to that of a modern bat due to a convergent development . In a bat, however, the flight membrane is only stretched between the fingers and arms; there is no additional spur in the area of the hands. However, bats have similar structures on their legs ( calcars ) and various gliders such as flying squirrels or the giant gliding pouch have cartilaginous or bony spurs.
The fossil was examined for the presence of melanosomes using an electron microscope at a total of twelve locations . Eumelanosomes, which cause a black color, were identified on all nine feather-bearing areas. Phaeomelanosomes were also found in the head feathers, which produce a more yellowish-brown tone. Phaeomelanosomes were identified in only one place on the flight membrane.
Paleobiology
Wing and flight reconstruction
Yi qi , and perhaps also representatives of other species of the Scansoriopterygidae, had wings of a type that was previously not known from any prehistoric species of dinosaurs or other bird-related species. Unlike other Paravias, they have replaced the bird-like feathers with membranous, bat-like wings.
These membranous wings of Yi qi are unique within the currently known dinosaurs and very difficult to interpret. The fact that the arm with the wing could in principle be used as a wing is shown by the fact that it is even longer than the already elongated rear extremity and the thickness of the long bones. In addition, it is difficult to find an alternative explanation for the long bone spur. The existence of this bone spur supports the thesis of the gliding membrane, since comparable elements can only be found in other animals specializing in gliding with corresponding membranes. Although bats in particular show a fluttering flight, the lack of appropriately developed muscles in the shoulder area also suggests a glider. Beyond that, no further knowledge about the nature of the flight of Yi qi can probably be concluded.
The authors of the first description by Xu Xing suggest three different models for the wing reconstruction of Yi qi . In the bat model, the bone spur of the wrist points straight down and, like a bat, a membrane spans between the spur and the body of the animal, forming a very broad wing. In a variant of this model, the pterosaur model, the spur points slightly downwards and spans a narrower wing. As the second main model, the Maniraptor model, the spur points towards the body and reinforces a narrow membrane that may have been broadened by feathers. As a final option, they propose a frog model in which the spur enlarges a membrane stretched between the toes and the spur, similar to that of today's flying frogs , and lacks a membrane to the body.
A first analysis of the flight characteristics of the bat model and the maniraptor model was carried out. In both cases, a wingspan of about two feet was assumed. The narrow wing of the Maniraptor resulted in a wing area of 320 cm² with a wing loading of 1.19 g / cm², with the wider bat model the wing area was 638 cm² with a wing loading of 0.6 g / cm². In both cases the wing loading was well below the 2.5 g / cm² critical for bird flight . In the case of the Maniraptor model, it corresponded to the load of a duck , which, however, has a larger wingspan and a smaller elongation . The load on the bat model corresponds to that of a typical sea bird, which, however, has a significantly larger wingspan and a higher aspect ratio.
One problem with the gliding hypothesis for Yi qi is the lack of the membrane along the body, which is typical for most glider pilots. The center of gravity of the animal was clearly behind the glide membranes and thus the main control, which makes the flight very unstable. The problem was perhaps solved by a short and fleshy tail with long tail feathers, as known from the Epidexipteryx . Alternatively, it could be released by fluttering the wing membrane, as in the flightless but gliding kakapo .
Paleoecology
The only previously known fossil of Yi qi was found in the rock of the Tiaojishan Formation , which is dated to the time of the Callovian to Oxfordian in the Middle to Late Jurassic 165 to 153 million years ago. It is about the same formation and thus about the same age at which other representatives of the Scansoriopterygidae such as Epidexipteryx and Scansoriopteryx were found.
The ecosystem of the Tiaojishan Formation was dominated by a forest of Bennettitales , ginkgo , conifers and ferns . The forests surrounded large lakes shaded by active volcanoes, the ash of which is responsible for the good preservation of many of the fossils found in the sites. Based on the composition of the vegetation, it is believed that the climate was humid and warm tropical to temperate. Other vertebrate fossils that were found in the same rock include Salamander as Chunerpeton tianyiensis that pterosaurs Changchengopterus pani , Dendrorhynchoides mutoudengensis and Qinglongopterus guoi and early arboreal mammal Arboroharamiya jenkinsi .
Discovery and systematics
The first and so far only fossil of Yi qi was found by farmer Wang Jianrong in a field near Mutoudeng Village , Qinglong County , Hebei . Wang sold the fossil in 2007 to Shandong Tianyu Museum of Nature, where technician Ding Xiaoqing carried out further preparation of the fossil. Since most of the unique features and soft tissue fossils were only uncovered in the museum, the editors assumed that the material was not a fake; this was later confirmed by computed tomography . The working group led by paleontologist Xu Xing published the results of their investigations and the first description in Nature in April 2015.
The genus Yi and thus also the species Yi qi was classified in the family Scansoriopterygidae within the Maniraptora . The exact relationship, especially to the other known genera of the Scansoriopterygidae, Epidendrosaurus and Epidexipteryx , has not yet been clarified. Within the Maniraptora, the position of the Scansoriopterygidae as the most basal group of the Paraves was consolidated.
The name was given by the first descriptor, using the genus name genus Yi based on the Chinese designation Chinese 翼 , Pinyin yì for "wing" and the species name qi based on Chinese 奇 , Pinyin qí for "strange". Since both names only consist of two letters and thus correspond to the minimum possible number according to rules 11.8.1 and 11.9.1 of the International Code of Zoological Nomenclature , the generic name is the shortest name so far given for a dinosaur and the entire species name, in addition to the name Ia io for the East Asian early nocturnal sailor , to one of the two shortest species names.
In May 2019, the description of another small species of dinosaur with bat-like wings was published. Ambopteryx longibrachium lived in the Upper Jurassic in what is now China, had hair-like proto-feathers and probably only weighed 200 g.
supporting documents
- ↑ a b c d e f g h i j k l m n o p q r X. Xu, X. Zheng, C. Sullivan, X. Wang, L. Xing, Y. Wang, X. Zhang, JK O ' Connor, F. Zhang, Y. Pan: A bizarre Jurassic maniraptoran theropod with preserved evidence of membranous wings . In: Nature . 521, 2015, pp. 70-3. doi : 10.1038 / nature14423 . PMID 25924069 .
- ↑ John Noble Wilford: Small Jurassic Dinosaur May Have Flown Without Feathers . In: New York Times , April 29, 2015.
- Jump up ↑ H. Zhang, M. Wang, X. Liu: Constraints on the upper boundary age of the Tiaojishan Formation volcanic rocks in West Liaoning-North Hebei by LA-ICP-MS dating . In: Chinese Science Bulletin . 53, No. 22, 2008, pp. 3574-3584. doi : 10.1007 / s11434-008-0287-4 .
- ↑ Wang Yongdonga, Saiki Ken'ichi, Zhang Wuc & Zheng Shaolin: Biodiversity and palaeoclimate of the Middle Jurassic floras from the Tiaojishan Formation in western Liaoning, China . In: Progress in Natural Science . 16, 2006, pp. 222-230. doi : 10.1080 / 10020070612330087 .
- ↑ Min Wang, Jingmai K. O'Connor, Xing Xu & Zhonghe Zhou: A new Jurassic scansoriopterygid and the loss of membranous wings in theropod dinosaurs. Nature, Volume 569, pages 256-259 (2019),
