Dinosaurs Live highlight 19: Pteranodon

Pteranodon (from Greek πτερ- "wing" and αν-οδων "toothless"), from the Late Cretaceous geological period of North America in present day Kansas, Alabama, Nebraska, Wyoming, and South Dakota, was one of the largest pterosaur genera and had a maximum wingspan of over 6 metres (20 ft). Pteranodon is known from more fossil specimens than any other pterosaur, with about 1,200 specimens known to science, many of them well preserved, with complete skulls and articulated skeletons. It was an important genus of the animal community present in the Western Interior Seaway.

Pteranodon was a reptile, but not a dinosaur. By definition, all dinosaurs belong to the groups Saurischia and Ornithischia, which excludes pterosaurs. Nevertheless, Pteranodon is frequently featured in dinosaur books and is strongly associated with dinosaurs by the general public.

Desription
Pteranodon species are extremely well represented in the fossil record, allowing for detailed descriptions of their anatomy and analysis of their life history. Over 1,000 specimens have been identified, though less than half are complete enough to give researchers good information on the anatomy of the animal. Still, this is more fossil material than is known for any other pterosaur, and it includes both male and female specimens of various age groups and, possibly, species.

Skull and beak
Unlike earlier pterosaurs such as Rhamphorhynchus and Pterodactylus, Pteranodon had toothless beaks, similar to those of modern birds. Pteranodon beaks were made of solid, bony margins that projected from the base of the jaws. The beaks were long, slender, and ended in thin, sharp points. The upper jaw was longer than the lower jaw. The upper jaw was curved upward; while this normally has been attributed only to the upward-curving beak, one specimen (UALVP 24238) has a curvature corresponding with the beak widening towards the tip. While the tip of the beak is not known in this specimen, the level of curvature suggests it would have been extremely long.

The most distinctive characteristic of Pteranodon is its cranial crest. These crests consisted of skull bones (frontals) projecting upward and backward from the skull. The size and shape of these crests varied due to a number of factors, including age, sex, and species. Male Pteranodon sternbergi, the older species of the two described to date (and sometimes placed in the distinct genus Geosternbergia), had a more vertical crest with a broad forward projection, while their descendants, Pteranodon longiceps, evolved a narrower, more backward-projecting crest. Females of both species were smaller and bore small, rounded crests. The crests were probably mainly display structures, though they may have had other functions as well.

Skeleton
Other distinguishing characteristics that set Pteranodon apart from other pterosaurs include narrow neural spines on the vertebrae, plate-like bony ligaments strengthening the vertebrae above the hip, and a relatively short tail in which the last few vertebrae are fused into a long rod. The entire length of the tail was about 3.5% as long as the wingspan, or up to 25 centimetres (9.8 in) in the largest males.