Editing Pteranodon (section)

===Revising species===
Williston was also the first scientist to critically evaluate all of the ''Pteranodon'' species classified by Cope and Marsh. He agreed with most of Marsh's classification, with a few exceptions. First, he did not believe that ''P. ingens'' and ''P. umbrosus'' could be considered synonyms, which even Cope had come to believe. He considered both ''P. velox'' and ''P. longiceps'' to be dubious; the first was based on non-diagnostic fragments, and the second, though known from a complete skull, probably belonged to one of the other, previously-named species. In 1903, Williston revisited the question of ''Pteranodon'' classification, and revised his earlier conclusion that there were seven species down to just three. He considered both ''P. comptus'' and ''P. nanus'' to be specimens of ''Nyctosaurus'', and divided the others into small (''P. velox''), medium (''P. occidentalis''), and large species (''P. ingens''), based primarily on the shape of their upper arm bones. He thought ''P. longiceps'', the only one known from a skull, could be a synonym of either ''P. velox'' or ''P. occidentalis'', based on its size.<ref name= bennett1994/>

In 1910, Eaton became the first scientist to publish a more detailed description of the entire ''Pteranodon'' skeleton, as it was known at the time. He used his findings to revise the classification of the genus once again based on a better understanding of the differences in pteranodont anatomy. Eaton conducted experiments using clay models of bones to help determine the effects of crushing and flattening on the shapes of the arm bones Williston had used in his own classification. Eaton found that most of the differences in bone shapes could be easily explained by the pressures of fossilization, and concluded that no ''Pteranodon'' skeletons had any significant differences from each other besides their size. Therefore, Eaton was left to decide his classification scheme based on differences in the skulls alone, which he assigned to species just as Marsh did, by their size. In the end, Eaton recognized only three valid species: ''P. occidentalis'', ''P. ingens'', and ''P. longiceps''.<ref name= bennett1994/>

The discovery of specimens with upright crests, classified by Harksen in 1966 as the new species ''[[Pteranodon sternbergi]]'', complicated the situation even further. prompting another revision of the genus by Halsey W. Miller in 1972. Because it was impossible to determine crest shape for all of the species based on headless skeletons, Miller concluded that all ''Pteranodon'' species except the two based on skulls (''P. longiceps'' and ''P. sternbergi'') must be considered ''[[nomen dubium|nomena dubia]]'' and abandoned. The skull Eaton thought belonged to ''P. ingens'' was placed in the new species ''Pteranodon marshi'', and the skull Eaton assigned to ''P. occidentalis'' was re-named ''Pteranodon eatoni''. Miller also recognized another species based on a skull with a crest similar to that of ''P. sternbergi''; Miller named this ''Pteranodon walkeri''. To help bring order to this tangle of names, Miller created three [[Subgenus|subgenera]]. ''P. marshi'' and ''P. longiceps'' were placed in the subgenus ''Longicepia'',<ref name=":0">{{Cite journal |last=Miller |first=Halsey W. |date=1972 |title=The taxonomy of the Pteranodon species from Kansas. |journal=Trans. Kans. Acad. Sci. |volume=74 |issue=1 |pages=1–19|doi=10.2307/3627663 |jstor=3627663 }}</ref> though this was later changed to simply ''Pteranodon'' due to the rules of priority.<ref>{{Cite journal |last=Miller |first=Halsey W. |date=1973 |title=Longicepia Miller (1972) preoccupied by Pteranodon Marsh. |journal=Trans. Kans. Acad. Sci. |volume=75 |issue=1 |pages=100|doi=10.2307/3627328 |jstor=3627328 }}</ref> ''P. sternbergi'' and ''P. walkeri'', the upright-crested species, were given the subgenus ''Sternbergia'',<ref name=":0" /> which was later changed to ''[[Geosternbergia]]'' because ''Sternbergia'' was preoccupied.<ref>{{Cite journal |last=Miller |first=Halsey W. |date=1973 |title=Geosternbergia. a new name for Sternbergia Miller, 1972; Non Paulo Couto 1970; non Jordan, 1925. |journal=J. Paleontol. |volume=52 |pages=194}}</ref> Finally, Miller named the subgenus ''Occidentalia'' for ''P. eatoni'', the skull formerly associated with ''P. occidentalis''. Miller further expanded the concept of ''Pteranodon'' to include ''[[Nyctosaurus]]'' as a fourth subgenus. Miller considered these to be an evolutionary progression, with the primitive ''Nyctosaurus'', at the time thought to be crestless, giving rise to small-crested ''Occidentalia'', which in turn gave rise to long-crested ''Pteranodon'', finally leading to tall-crested ''Geosternbergia''.<ref name=":0" /> However, Miller made several mistakes in his study concerning which specimens Marsh had assigned to which species, and most scientists disregarded his work on the subject in their later research.<ref name="bennett1994" /> In 1984, Robert Milton Schoch published another revision that essentially returned to Marsh's original classification scheme, most notably sinking ''P. longiceps'' as a synonym of ''P. ingens''.<ref>{{Cite journal |last=Schoch |first=Robert Milton |date=1984 |title=Notes on the Type Specimens of Pteranodon and Nyctosaurus (Pterosauria, Pteranodontidae) In the Yale Peabody Museum Collections |url=https://elischolar.library.yale.edu/cgi/viewcontent.cgi?article=1193&context=peabody_museum_natural_history_postilla |journal=Postilla |volume=194 |pages=1–23}}</ref>