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
Methods used to estimate the mass of large male "Pteranodon" specimens (those with wingspans of about 7 meters) have been notoriously unreliable, producing a wide range of estimates from as low as to as high as . In a review of pterosaur size estimates published in 2010, researchers Mark Witton and Mike Habib demonstrated that the latter, largest estimates are almost certainly incorrect given the total volume of a "Pteranodon" body, and could only be correct if the animal "was principally aluminium". Witton and Habib considered the methods used by researchers who obtained smaller mass estimates equally flawed. Most have been produced by scaling modern animals such as bats and birds up to "Pteranodon" size, despite the fact that pterosaurs have vastly different body proportions and soft tissue anatomy from any living animal.