Yi (dinosaur)
| Yi | |
|---|---|
| |
| Replica fossil of Y. qi | |
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Family: | †Scansoriopterygidae |
| Genus: | †Yi Xu et al., 2015 |
| Type species | |
| Yi qi Xu et al., 2015
| |
| Species | |
| |
Yi is a genus of
Discovery and naming
The first and only known fossil specimen of Yi qi was found by a farmer, Wang Jianrong, in a quarry near Mutoudeng Village (
The team of scientists who authored this initial study were led by Xu Xing and also included Zheng Xiaoting, Corwin Sullivan, Wang Xiaoli, Xing Lida, Wang Yan, Zhang Xiaomei, Jingmai O'Connor, Zheng Fucheng Zhang and Pan Yanhong. They named and described the type species Yi qi. The generic name Yi means "wing" in Mandarin. The specific name qi means "strange".[1] Yi is notable for having the shortest generic name of any dinosaur, containing only two letters. Its binomial name, Yi qi, is also the shortest possible under articles 11.8.1 and 11.9.1 of the International Code of Zoological Nomenclature, at four letters. (It shares this distinction with the great evening bat Ia io.)
Description
Yi qi is known only from a single partial skeleton (holotype specimen STM 31-2) currently in the collections of the Shandong Tianyu Museum of Nature. The fossil was compressed and is visible on a stone plate and a counterplate. It is largely articulated, including the skull, lower jaws, neck and limb bones but lacking most of the backbone, pelvis and tail. Yi was a relatively small animal, estimated to weigh about 380 grams (0.84 lb).[1]
Like other scansoriopterygids, the head was short and blunt-snouted, with a downturned lower jaw. Its few teeth were present only in the tips of the jaws, with the four upper front teeth per side being the largest and slightly forward-pointing, and the front lower teeth being angled even more strongly forward.[1] The long, slender forelimbs were similar, overall, to those of most other paravian dinosaurs. Like other scansoriopterygid dinosaurs, the first finger was shortest and the third was the longest. Unlike all other known dinosaurs, a long, pointed wrist bone known as a "styliform element", exceeding both the third finger and the ulna in length, extended backward from the forelimb bones. This styliform, an adaptation to help support the membrane, may have been a newly evolved wrist bone, or a calcified rod of cartilage. It was slightly curved and tapered at its outer end.[1]
The only known specimen of Yi qi preserved a heavy covering of feathers. Unusually, based on its classification as an advanced
Small patches of wrinkled skin were also preserved, between the fingers and the styliform bone, indicating that unlike all other known dinosaurs, the planes of Yi qi were formed by a skin membrane rather than flight feathers.
On twelve positions the fossil was checked by an
Classification
Yi was placed in the
Paleobiology
Yi qi, and presumably other scansoriopterygids, possessed a type of wing unknown among any other prehistoric bird relatives. Unlike other paravian dinosaurs, they seem to have replaced bird-like feathers with membranous wings, in what may have been one of many independent evolutionary experiments with flight close to the origin of birds. The membranous wings of Yi qi are unique among dinosaurs and difficult to interpret. That the arm could in principle function as a wing, is shown by being longer than the already elongated hindlimb and the sufficient thickness of its long bones. Also it is hard to explain the styliform element outside a flight context. The presence of a long styliform bone adding support to the membrane, found only in other animals that glide, suggests that Yi qi was specialized for gliding flight. While it is possible that some form of flapping flight was also used by this animal, the lack of evidence for large pectoral muscles—the deltopectoral crest of the humerus being small—and the cumbersome nature of the styliform, make it more likely that Yi qi was an exclusive glider. At best, the researchers who conducted the initial study of the only known Yi specimen concluded that its mode of flight should be considered uncertain.[1]
The authors proposed three main models for the wing configuration. In the "bat model", the styliform element would have pointed straight to the rear, a membrane connecting styliform and torso. This would have resulted in a broad wing. A variant of the bat model might be the "pterosaur model" in which the styliform bone would have been directed obliquely to the outside, with a narrower wing as a result. The second main possibility is the "maniraptor model", in which the styliform element was pointing towards the body, reinforcing the trailing edge of a narrow membrane, possibly widened by feathers, on the top or the underside, sticking out. A last configuration would be the "frog model", the styliform bone enlarging a membranous hand plane, like that used by
A preliminary analysis was made of the flight characteristics of the bat model and the maniraptor model. For both models it was assumed that the wingspan was about sixty centimetres (24 in). The narrow wing of the maniraptor model would have resulted in a 320 cm2 (50 sq in) wing surface with a
In 2020, T. Alexander Dececchi and colleagues found that, though Yi and other scansoriopterygids were
Paleoecology
The only known Yi qi fossil was found in rocks assigned to the
See also
References
- ^ S2CID 205243599.
- ^ Wilford, John Noble (April 29, 2015). "Small Jurassic Dinosaur May Have Flown Without Feathers". The New York Times. Archived from the original on 2 November 2017. Retrieved April 29, 2015.
- PMID 33376962.
- S2CID 212957272.
- doi:10.1080/10020070612330087A (inactive 31 January 2024). Archived from the original on 13 February 2021. Retrieved 29 May 2020.)
{{cite journal}}: CS1 maint: DOI inactive as of January 2024 (link - S2CID 4466953.
External links
