Gansus
| Gansus Temporal range: Early Cretaceous, 110 Ma |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| (unranked): | Ornithurae |
| Order: | Gansiformes |
| Family: | Gansidae |
| Genus: | Gansus Hou & Liu, 1984 |
| Species | |
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Gansus is a genus of aquatic birds that lived during the Aptian or Albian age of the Early Cretaceous period (somewhere between 115 to 105 million years ago) in what is now Gansu province, western China. It is the oldest-known of the Ornithurae, the group which includes modern birds (Neornithes) and extinct related groups, such as Ichthyornis and Hesperornithes.
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[edit] Description
The genus Gansus contains a single species, G. yumenensis,[2] which was about the size of a pigeon and similar in appearance to loons and diving ducks. [3] It had many features common among modern birds, and also retained some primitive traits such as its clawed wings.[4]
Gansus was discovered in the form of a single fossil foot in 1981. Five more well-preserved fossils were found in 2003–2004 in mudstone at the site of an ancient lake at Changma, Gansu; the geological stratum in which the fossils were found is the Xiagou Formation. Their bodies had settled in anoxic mud and were soon covered with further extremely fine silty sediments. Without oxygen, their remains resisted decay: these specimens preserved remains of flight feathers and traces of the webbing between their toes.[5]
[edit] Classification
Gansus was described as the oldest known ornithuran. The Ornithurae, however, has been given several very different definitions. In the definition used by You and colleagues (that is, the clade containing all living birds plus Hesperornis and Ichthyornis), Gansus is indeed the oldest known member. However, several birds from the older Yixian Formation and Jiufotang Formation are considered ornithurans under other definitions. Under any definition, all living birds, including taxa as diverse as ostriches, hummingbirds and eagles, are descended from basal ornithurans, many of which were semi-aquatic. It is now thought possible that all modern birds descended specifically from a semi-aquatic bird similar to Gansus. Thus, while Gansus is not necessarily a direct ancestor of today's birds, it is closely related to such an ancestral species.[4]
[edit] References
- ^ http://www.ploscollections.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0025494;jsessionid=FA97A351C38FAC34F759E74509346C5F.ambra01
- ^ Hou, L. & Liu, Z. (1984): A new fossil bird from Lower Cretaceous of Gansu and early evolution of birds. Sci. Sin. Ser. B 27: 1296−1302.
- ^ MSNBC (2006-06-15). "Waterfowl fossils fill in a big missing link: 110 million-year-old birds bridge gap between age of dinosaurs and today". http://msnbc.msn.com/id/13342029. Retrieved 2006-06-15.
- ^ a b You, Hai-lu; Lamanna, Matthew C.; Harris, Jerald D.; Chiappe, Luis M.; O'Connor, Jingmai; Ji, Shu-an; Lü, Jun-chang; Yuan, Chong-xi; Li, Da-qing; Zhang, Xing; Lacovara, Kenneth J.; Dodson, Peter & Ji, Qiang (2006): "A Nearly Modern Amphibious Bird from the Early Cretaceous of Northwestern China." Science 312: 1640-1643. doi:10.1126/science.1126377 Supporting Online Material
- ^ Norris, Scott (2006-06-15). "Dinosaur-Era Birds Surprisingly Ducklike, Fossils Suggest". National Geographic Society. http://news.nationalgeographic.com/news/2006/06/060615-dinosaurs.html. Retrieved 2006-06-15.
[edit] External links
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