Editing Pteranodon (section)

==Discovery and history==
[[File:Ornithochirus umbrosus.jpg|thumb|left|Early illustration of ''Ornithocheirus umbrosus'' (now ''Pteranodon''), when teeth erroneously were attributed to the species and the crest was unknown, 1872]]

===First fossils===
''Pteranodon'' was the first pterosaur found outside of [[Europe]]. Its fossils first were found by [[Othniel Charles Marsh]] in 1871,<ref>{{Cite journal|last=Witton|first=Mark Paul|date=2010|title=Pteranodon and beyond: The history of giant pterosaurs from 1870 onwards|url=https://www.researchgate.net/publication/258391482|journal=Geological Society, London, Special Publications|volume=343|issue=1|pages=313–323|doi=10.1144/SP343.19|bibcode=2010GSLSP.343..313W|s2cid=128801077|via=ResearchGate}}</ref> in the Late Cretaceous [[Smoky Hill Chalk]] deposits of western Kansas. These [[chalk]] beds were deposited at the bottom of what was once the [[Western Interior Seaway]], a large shallow sea over what now is the midsection of the North American continent. These first specimens, YPM 1160 and YPM 1161, consisted of partial wing bones, as well as a tooth from the prehistoric fish ''[[Xiphactinus]]'', which Marsh mistakenly believed to belong to this new pterosaur (all known pterosaurs up to that point had teeth). In 1871, Marsh named the find ''Pterodactylus oweni'', assigning it to the well-known (but much smaller) European [[genus]] ''[[Pterodactylus]]''. Marsh also collected more wing bones of the large pterosaur in 1871. Realizing that the name he had chosen had already been used for Harry Seeley's European pterosaur species ''[[Pterodactylus oweni]]'' in 1864, Marsh renamed his giant North American pterosaur ''Pterodactylus occidentalis'', meaning "Western wing finger," in his 1872 description of the new specimen. He named two additional species, based on size differences: ''Pterodactylus ingens'' (the largest specimen so far), and ''Pterodactylus velox'' (the smallest).<ref name= bennett1994/>

Meanwhile, Marsh's rival [[Edward Drinker Cope]] had unearthed several specimens of the large North American pterosaur. Based on these specimens, Cope named two new species, '''''Ornithochirus umbrosus''''' and ''Ornithochirus harpyia'', in an attempt to assign them to the large European genus ''[[Ornithocheirus]]'', though he misspelled the name (forgetting the 'e').<ref name=bennett1994/> Cope's paper naming his species was published in 1872, just five days after Marsh's paper. This resulted in a dispute, fought in the published literature, over whose names had priority in what obviously were the same species.<ref name=bennett1994/> Cope conceded in 1875 that Marsh's names did have priority over his, but maintained that ''Pterodactylus umbrosus'' was a distinct species (but not genus) from any that Marsh had named previously.<ref name=cope1875>Cope, E.D. (1875). "The Vertebrata of the Cretaceous formations of the West." ''Report, U. S. Geological Survey of the Territories (Hayden)'', '''2''': 302 pp., 57 pls.</ref> Re-evaluation by later scientists has supported Marsh's case, refuting Cope's assertion that ''P. umbrosus'' represented a larger, distinct species.<ref name=bennett1994/>

===A toothless pterosaur===
[[File:Pteranodon longiceps YPM1177.jpg|thumb|left|Short-crested ''P. longiceps'' holotype specimen YPM1177, now interpreted as a female individual]]

While the first ''Pteranodon'' wing bones were collected by Marsh and Cope in the early 1870s, the first ''Pteranodon'' skull was found on May 2, 1876, along the [[Smoky Hill River]] in [[Wallace County, Kansas|Wallace County]] (now Logan County), Kansas, USA, by [[Samuel Wendell Williston]], a fossil collector working for Marsh.<ref name= "bennett2000">Bennett, S.C. (2000). "Inferring stratigraphic position of fossil vertebrates from the Niobrara Chalk of western Kansas." ''Current Research in Earth Sciences: Kansas Geological Survey Bulletin'', '''244'''(Part 1): 26 pp.</ref> A second, smaller skull soon was discovered as well. These skulls showed that the North American pterosaurs were different from any European species, in that they lacked teeth and had bony crests on their skulls. Marsh recognized this major difference, describing the specimens as "distinguished from all previously known genera of the order Pterosauria by the entire absence of teeth." Marsh recognized that this characteristic warranted a new genus, and he coined the name ''Pteranodon'' ("wing without tooth") in 1876. Marsh reclassified all the previously named North American species from ''Pterodactylus'' to ''Pteranodon''. He considered the smaller skull to belong to ''Pteranodon occidentalis'', based on its size. Marsh classified the larger skull, YPM 1117, in the new species ''Pteranodon longiceps'', which he thought to be a medium-sized species in between the small ''P. occidentalis'' and the large ''P. ingens''.<ref name=marsh1876a>{{Cite journal | last = Marsh| first= O.C. | year = 1876a | title = Notice of a new sub-order of Pterosauria | url = https://zenodo.org/record/1450032| journal = American Journal of Science |series=Series 3 | volume = 11 | issue = 65| pages = 507–509 | doi=10.2475/ajs.s3-11.66.507| bibcode= 1876AmJS...11..507M | s2cid = 130203580 }}</ref><ref name=bennett1994/> Marsh also named several additional species: '''''Pteranodon comptus''''' and ''[[Pteranodon nanus]]'' were named for fragmentary skeletons of small individuals, while ''Pteranodon gracilis'' was based on a wing bone that he mistook for a pelvic bone. He soon realized his mistake, and re-classified that specimen again into a separate genus, which he named ''[[Nyctosaurus]]''. ''P. nanus'' was also later recognized as a ''Nyctosaurus'' specimen.<ref name=marsh1976b>{{Cite journal |  last= Marsh | first= O.C. | year = 1876b | title = Principal characters of American pterodactyls | url = https://zenodo.org/record/1450034| journal = American Journal of Science |series=Series 3 | volume = 12 | issue = 72| pages = 479–480 | doi=10.2475/ajs.s3-12.72.479| bibcode= 1876AmJS...12..479M | s2cid = 131057784 }}</ref><ref name=bennett1994/>

In 1892, Samuel Williston examined the question of ''Pteranodon'' classification. He noticed that, in 1871, Seeley had mentioned the existence of a partial set of toothless pterosaur jaws from the [[Cambridge Greensand]] of [[England]], which he named ''[[Ornithostoma]]''. Because the primary characteristic Marsh had used to separate ''Pteranodon'' from other pterosaurs was its lack of teeth, Williston concluded that "Ornithostoma" must be considered the senior synonym of ''Pteranodon''. However, in 1901, Pleininger pointed out that "Ornithostoma" had never been scientifically described or even assigned a species name until Williston's work, and therefore had been a ''[[nomen nudum]]'' and could not beat out ''Pteranodon'' for naming priority. Williston accepted this conclusion and went back to calling the genus ''Pteranodon''.<ref name= bennett1994/> However, both Williston and Pleininger were incorrect, because unnoticed by both of them was the fact that, in 1891, Seeley himself had finally described and properly named ''Ornithostoma'', assigning it to the species ''O. sedgwicki''. In the 2010s, more research on the identity of ''Ornithostoma'' showed that it was probably not ''Pteranodon'' or even a close relative, but may in fact have been an [[Azhdarchoidea|azhdarchoid]], a different type of toothless pterosaur.<ref name=Averianov2012>{{cite journal | last1 = Averianov | first1 = A.O. | year = 2012 | title = ''Ornithostoma sedgwicki'' – valid taxon of azhdarchoid pterosaurs | journal = Proceedings of the Zoological Institute RAS | volume = 316 | issue = 1 | pages = 40–49| doi = 10.31610/trudyzin/2012.316.1.40 | s2cid = 67809186 | doi-access = free }}</ref>

===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>

===Recognizing variation===
In the late 1980s and early 1990s, S. Christopher Bennett published several major papers reviewing the anatomy, taxonomy and life history of ''Pteranodon''.<ref name= kellner2010/> In 1992, he published a paper discussing [[sexual dimorphism]] and its role in individual variation among ''Pteranodon'' fossils, a follow-up of a 1987 paper he authored on the same subject.<ref name=":1">{{Cite journal |last=Bennett |first=S. Christopher |date=1987 |title=Sexual dimorphism in the pterosaur Pteranodon. |journal=Journal of Vertebrate Paleontology |volume=7}}</ref> In the 1992 paper, he referred only to two species, ''P. longiceps'' and ''P. sternbergi''.<ref name="bennett1992" /> Two years later, he published a paper fully revising its taxonomy, wherein he concluded that only ''P. longiceps'' and ''P. sternbergi'' were valid species. ''P. marshi'' and ''P. walkeri'' were regarded as junior synonyms of ''P. longiceps'', and ''P. eatoni'' as a junior synonym of ''P. stenbergi''. The remainder were either rendered ''nomina dubia'' or placed in Nyctosaurus''.''<ref name="bennett1994" />