Pteranodon
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 (now Logan County), Kansas, USA, by Samuel Wendell Williston, a fossil collector working for Marsh. 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". 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.
Pteranodon
In 2010, pterosaur researcher Alexander Kellner revisited H.W. Miller's classification. Kellner followed Miller's opinion that the differences between the "Pteranodon" species were great enough to place them into different genera. He placed "P. sternbergi" into the genus named by Miller, "Geosternbergia", along with the Pierre Shale skull specimen which Bennett had previously considered to be a large male "P. longiceps". Kellner argued that this specimen's crest, though incompletely preserved, was most similar to "Geosternbergia". Because the specimen was millions of years younger than any known "Geosternbergia", he assigned it to the new species "Geosternbergia maysei". Numerous other pteranodont specimens are known from the same formation and time period, and Kellner suggested they may belong to the same species as "G. maysei", but because they lack skulls, he could not confidently identify them.