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.
Rhenanida
The fossil record of Rhenanida is very sparse, with most fossils being isolated tubercles and skull fragments that are identified as being similar to "Gemuendina stuertzi", the most well-known rhenanid, known from several specimens from the Hunsruck slates. Given the rhenanids' worldwide distribution, this paupacity probably did not reflect a scarcity of living individuals (when the order was alive), but reflects the fact that rhenanid armor disintegrated into isolated fragments, and scattered soon after the owner's demise. Most fossils of rhenanids are from the Early Devonian, primarily in the United States and Germany. The recently discovered "Nefudina qalibahensis" is known from Northeastern Saudi Arabia. "Asterosteus stenocephalus" is known from Mid Devonian Ohio. Another species of rhenanid was "Bolivosteus chacomensis", of the Lower to Middle Devonian Malvinokaffric Fauna of Western Gondwana, in what is now Bolivia, South America. The youngest rhenanid, "Jagorina pandora" is known from Upper Devonian Germany.