Gansus

Taxobox
name = "Gansus"
fossil_range = Early Cretaceous
regnum = Animalia
phylum = Chordata
classis = Aves
ordo = Gansuiformes
familia = Gansuidae
genus = "Gansus"
genus_authority = Hou & Liu, 1984
binomial = "Gansus yumenensis"
binomial_authority = Hou & Liu, 1984

"Gansus" is a genus of aquatic birds that lived during the Albian stage of the Early Cretaceous period (around 110 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 "Ichthyornithes" and "Hesperornithes".

The genus contains a single species, "G. yumenensis", which was about the size of a pigeon and similar in appearance to loons and diving ducks.cite web|url=http://msnbc.msn.com/id/13342029|title=Waterfowl fossils fill in a big missing link: 110 million-year-old birds bridge gap between age of dinosaurs and today|author=MSNBC|date=2006-06-15|accessdate=2006-06-15] It had most modern bird features, with exceptions such as its clawed wingtips and its lack of hollow bones, both of which may have impaired its flight slightly.

The Ornithurae form a clade which contains all living birds and their closest relatives). "All" extant birds, including taxa as diverse as ostriches, hummingbirds and eagles, are descended from basal Ornithurans. It is now thought entirely possible that all 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. It is the oldest modern bird known to date. A thorough comparison of "G. yumenensis" to the Hesperornithes may prove especially fruitful, as the assignment of the latter to the Ornithurae is not altogether certain because of their extreme specialization (e.g. their feet that were carried splayed sidewards and their near-complete loss of wings).

"Gansus" was discovered in the form of a single fossil foot in 1981. Then five 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.cite web|url=http://news.nationalgeographic.com/news/2006/06/060615-dinosaurs.html|title=Dinosaur-Era Birds Surprisingly Ducklike, Fossils Suggest|first=Scott|last=Norris|publisher=National Geographic Society|date=2006-06-15|accessdate=2006-06-15]

References

*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.
*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 [http://dx.doi.org/10.1126/science.1126377 HTML abstract] [http://www.sciencemag.org/cgi/content/full/312/5780/1640/DC1 Supporting Online Material]
*http://www.theglobeandmail.com/servlet/story/RTGAM.20060615.woldbird0615/BNStory/Science/home

Footnotes