Editing Pteranodon (section)

===Timespan and evolution===
[[File:Pteranodon longiceps launch.jpg|thumb|Skeleton of ''P. longiceps'', in launch pose, [[Telus World of Science, Vancouver]]]]
''Pteranodon'' fossils are known primarily from the [[Niobrara Formation]] of the central United States. Broadly defined, ''Pteranodon'' existed for more than four million years, during the [[Santonian]] stage of the [[Cretaceous]] period.<ref name=bennett1994>{{Cite journal | author = Bennett, S.C. | year = 1994 | title = Taxonomy and systematics of the Late Cretaceous pterosaur ''Pteranodon'' (Pterosauria, Pterodactyloida) | journal = Occasional Papers of the Natural History Museum, University of Kansas | volume = 169 | pages = 1–70}}</ref> The genus is present in most layers of the Niobrara Formation except for the upper two; in 2003, [[Kenneth Carpenter]] surveyed the distribution and dating of fossils in this formation, demonstrating that ''Pteranodon sternbergi'' existed there from 88 to 85 million years ago, while ''P. longiceps'' existed between 86 and 84.5 million years ago. A possible third species, which Kellner named ''[[Geosternbergia|Geosternbergia maiseyi]]'' in 2010, is known from the Sharon Springs member of the [[Pierre Shale Formation]] in Kansas, [[Wyoming]], and [[South Dakota]], dating to between 81.5 and 80.5 million years ago.<ref name=carpenter2003>{{cite journal | last1 = Carpenter | first1 = K | year = 2003 | title = Vertebrate Biostratigraphy of the Smoky Hill Chalk (Niobrara Formation) and the Sharon Springs Member (Pierre Shale) | journal = High-Resolution Approaches in Stratigraphic Paleontology | volume = 21 | pages = 421–437 | doi = 10.1007/978-1-4020-9053-0 | series = Topics in Geobiology | isbn = 978-1-4020-1443-7}}</ref>

In the early 1990s, Bennett noted that the two major [[Polymorphism (biology)|morphs]] of pteranodont present in the Niobrara Formation were precisely separated in time with little, if any, overlap. Due to this, and to their gross overall similarity, he suggested that they probably represent [[chronospecies]] within a single evolutionary lineage lasting about 4 million years. In other words, only one species of ''Pteranodon'' would have been present at any one time, and ''P. sternbergi'' (or ''Geosternbergia'') in all likelihood was the direct ancestor species of ''P. longiceps''.<ref name=bennett1994niobrara/>