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 ornithuran, the group which includes modern birds and their extinct relatives, such as Ichthyornis and Hesperornis. The Early Cretaceous (timestratigraphic name) or the Lower Cretaceous (logstratigraphic name), is the earlier of the two major divisions of the Cretaceous period. ... Scientific classification or biological classification is how biologists group and categorize extinct and living species of organisms (as opposed to folk taxonomy). ... Phyla Subregnum Parazoa Porifera (sponges) Subregnum Agnotozoa Placozoa (trichoplax) Orthonectida (orthonectids) Rhombozoa (dicyemids) Subregnum Eumetazoa Radiata (unranked) (radial symmetry) Ctenophora (comb jellies) Cnidaria (coral, jellyfish, anemones) Bilateria (unranked) (bilateral symmetry) Acoelomorpha (basal) Orthonectida (parasitic to flatworms, echinoderms, etc. ... Typical Classes Subphylum Urochordata - Tunicatas Ascidiacea Thaliacea Larvacea Subphylum Cephalochordata - Lancelets Subphylum Myxini - Hagfishes Subphylum Vertebrata - Vertebrates Petromyzontida - Lampreys Placodermi (extinct) Chondrichthyes - Cartilaginous fishes Acanthodii (extinct) Actinopterygii - Ray-finned fishes Actinistia - Coelacanths Dipnoi - Lungfishes Amphibia - Amphibians Reptilia - Reptiles Aves - Birds Mammalia - Mammals Chordates (phylum Chordata) include the vertebrates, together with... Orders Many - see section below. ... 1984 (MCMLXXXIV) was a leap year starting on Sunday of the Gregorian calendar. ... In biology, binomial nomenclature is the formal method of naming species. ... 1984 (MCMLXXXIV) was a leap year starting on Sunday of the Gregorian calendar. ... In biology, a genus (plural genera) is a taxonomic grouping. ... Orders Many - see section below. ... Albian (Fr. ... The Cretaceous period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic period, about 146 million years ago (Ma), to the beginning of the Paleocene epoch of the Tertiary period (65. ... In astronomy, geology, and paleontology, mya is an acronym for million years ago and is used as a unit of time to denote length of time before the present. ... Gansu (Simplified Chinese: 甘肃; Traditional Chinese: 甘肅; Hanyu Pinyin: ; Wade-Giles: Kan-su, Kansu, or Kan-suh) is a province located in the northwest of the Peoples Republic of China. ... This article does not cite its references or sources. ... Families Hesperornithidae Hesperornithiformes are an extinct and highly specialized order of Cretaceous toothed birds. ...

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.^[1] It had most modern bird features, with exceptions such as its lack of hollow bones, and its clawed wingtips, both of which may have impaired its flight slightly. This bird is the oldest-known member of the Ornithurae (a clade which contains all living birds and their closest relatives); and is the earliest known example of that group. Subfamily Columbinae Otidiphabinae Gourinae Didunculinae Treroninae Pigeon beside Weiming Lake, Peking University (2002) The doves are the 308 species of near passerine birds in the order Columbiformes. ... Species Gavia stellata Gavia arctica Gavia pacifica Gavia immer Gavia adamsii The loon (N.Am. ... Genera Marmaronetta Netta (including Rhodonessa) Aythya † See also dabbling duck The 16 species of diving duck, also known as pochards, make up a sub-group of the biological subfamily Anatinae, which itself is part of the diverse and very large duck, goose and swan family, Anatidae. ... For a list of birds extinct in Late Quaternary prehistoric times and (usually) known from specimens not completely fossilized, see Later Quaternary Prehistoric Birds. ... A clade is a term belonging to the discipline of cladistics. ...

All extant birds, including taxa as diverse as ostriches 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 taxon (plural taxa), or taxonomic unit, is a grouping of organisms (named or unnamed). ... Binomial name Struthio camelus Linnaeus, 1758 The ostrich (Struthio camelus) is a flightless bird native to Africa. ... Genera Eagles are large birds of prey, who inhabit mainly the Old World, with only two species (Bald Eagle and Golden Eagle) in North America, a few in South America and three (White-bellied Sea Eagle, Little Eagle and Wedge-tailed Eagle) in Australia. ...

Previously known from only a single fossil foot discovered in 1981, five well-preserved Gansus 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 are 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.^[2] Mudstone is a fine-grained sedimentary rock whose original constituents were clays or muds. ... Remiges are a birds flight feathers which are attached to the rear portion of the wing bones. ...

Notes

1. ^ 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. Retrieved on 2006-06-15.
2. ^ Norris, Scott (2006-06-15). Dinosaur-Era Birds Surprisingly Ducklike, Fossils Suggest. National Geographic Society. Retrieved on 2006-06-15.

The current version of the article or section reads like an advertisement. ... 2006 (MMVI) is a common year starting on Sunday of the Gregorian calendar. ... June 15 is the 166th day of the year in the Gregorian calendar (167th in leap years), with 199 days remaining. ... 2006 (MMVI) is a common year starting on Sunday of the Gregorian calendar. ... June 15 is the 166th day of the year in the Gregorian calendar (167th in leap years), with 199 days remaining. ... 2006 (MMVI) is a common year starting on Sunday of the Gregorian calendar. ... June 15 is the 166th day of the year in the Gregorian calendar (167th in leap years), with 199 days remaining. ... Flag of the National Geographic Society The National Geographic Society, is a not-for-profit scientific organization based in the United States. ... 2006 (MMVI) is a common year starting on Sunday of the Gregorian calendar. ... June 15 is the 166th day of the year in the Gregorian calendar (167th in leap years), with 199 days remaining. ...

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 HTML abstract Supporting Online Material
• http://www.theglobeandmail.com/servlet/story/RTGAM.20060615.woldbird0615/BNStory/Science/home