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.
Pisanosaurus
"Pisanosaurus" is known from a single fragmented skeleton discovered in 1962 by Galileo Juan Scaglia at the Agua de Las Catas locality in the Ischigualasto Formation, in La Rioja, Argentina. It is based on a specimen given the designation PVL 2577, which consists of a partial skull with a fragmentary right maxilla with teeth, and incomplete right mandibular ramus (lower jaw), six incomplete cervical vertebrae, seven incomplete dorsal vertebrae, molds of five sacral vertebrae, a rib and several rib fragments, a fragmentary right scapula, a coracoid, molds of a fragmentary ilium, ischium and pubic bone, an impression of three metacarpals, the complete femora, the right tibia, the right fibula, with an articulated astragalus and calcaneum, a tarsal element with a metatarsal, metatarsals III and IV, three phalanges from the third toe and five phalanges, among them the ungual, from the fourth toe, and an indeterminate long bone fragment.