Pteranodon

Pteranodon longiceps. Credit: Julio Lacerda.

*Pteranodon* is an extinct genus of pterosaur that lived during the Late Cretaceous in North America.

## History

While the first *Pteranodon* were collected by Marsh and Cope in the early 1870s, the first skull was found on May 2, 1876 along the Smoky Hill River by Samuel Wendell Williston. Another skull, smaller, was found as well; these differentiated North American from European pterosaur biota. Marsh (1876) found it may represent a new genus, naming it *Pteranodon* based on the lack of teeth and he bony crests. Among these, he reassigned YPM 1117 to *P. longiceps* and named many species now recognized as invalid.

## Description

The head of *Pteranodon* is fitted with a large beak and head crest. Scientists estimate the head crest was used for either steering in the air or for display. Sexual dimorphism in specimens is not unusual. Sizes vary between males and females greatly so it is hard to find a good answer to their height, weight and wingspans. Two species of *Pteranodon* exist currently, *P. longiceps* and *P. sternbergi*. *Pteranodon sternbergi*, or *Geosternbergia*, is doubted. Many scientists doubt the pterosaur *Dawndraco*, wanting to reclassify it to be synonymous with the *Pteranodon* genus. *Pteranodon* is among the most common pterosaur genera. Many specimens of *Pteranodon* are known, having nearly 1000 specimens identified and many details of their anatomical and life history known. This is far greater than any other pterosaur species, and are from different age ranges, species and genders.

Adult *Pteranodon* individuals of both valid species can be divided into two size classes. The smaller size class is differentiated from a shorter and rounded crest and pelvic canals wider than in the opposite class. These canals are likely to accommodate to laying eggs, making smaller adults females. The larger size class have narrow hips and large crests, likely to display.
Adult male *Pteranodon* were some of the largest recorded pterosaurs and flying animals in the 20th century until the discovery of azhdarchids. The average mature male has a wingspan of 5.6 meters (18 feet), with mature females averaging 3.8 meters (12 feet). The largest *P. longiceps* from the Niobrara Formation measures 6.25 meters (20.5 feet) from one wingtip to the other. A specimen from the Pierre Shale Formation may have measured 7.25 meters (23.8 feet) long, but may belong to the genus *Geosternbergia*. Most specimens are found crushed and deformed, but enough remains attributed to *Pteranodon* exist to piece together the animal in life.

Methods used to estimate *Pteranodon* specimens with large wingspans such as 7 meters are unreliable, producing a range of 20-93 kilograms 944-205 pounds). Mark Witton and Mike Habib (2010) found the largest of that range are likely incorrect due to their total volume, and could only be correct if the animal were mainly made of aluminium. They considered methods used to find smaller estimates, finding they were equally wrong. Most are produced by using bats and birds scaled to size, which is also flawed since their bauplans are extremely different. Narrow neural spines, plate-like bony ligaments above the hip and a short tail comprised by the last vertebrae fused into a rod differentiate *Pteranodon*. The tail is ~3.5% of the wingspan, up to 25 centimeters (9.8 inches) in the largest males.

It bore toothless jaws unlike early pterosaurs, made of solid and bony margins that project from the jaw's base. The beaks are elongate and slender, ending in a thin point, with the upper jaw overhanging the lower. The upper jaw also curves up, with UALVP 24238 widening at the beak tip, although the tip is not known, it possesses extreme curvature that implies a long length and widening. Alexander Kellner (2010) assigned this to a new genus, which has been synonymized. The crest consisted from frontals that project up and back, varying in shape depending on age, sex and species. Species traditionally known as *Geosternbergia* (*P. sternbergi*?) have a more vertical and broad forward projection, with *P. longiceps* have a narrower and more backwards-projecting crest. Females of both species were smaller and had smaller, rounded crests. Such crests were likely display structures, but they may have had another function nonetheless.

 File:Private pteranodon.png  One specimen of a *Pteranodon* sp. was collected by Ken Jenkins in the late 1990s or early 2000s. Its exact stratigraphic data is unknown, however, since the specimen was immediately placed into the hands of an auction house. The auction "enhanced" the specimen, which was originally represented by a since top jaw and fragmented crest, painting in a mandible and filling in the missing material. However, this specimen, since it is unavailable for study, was unable to be informally identified, so many refer to it as *Pteranodon* sp..

## Paleobiology

### Flight

Wing shape suggests a flight style similar to the albatross based on the high aspect ratio. It would have had to soar, having a rapid burst of flapping (of which it could sustain a substantial amount). One recent study suggests it relies on thermal soaring much like continental flyers and *Pelagornis*. It took flight from a standing position, using their forelimbs as leverage to leap into the air via a high amount of generated energy. The wings would upstroke once the animal was a considerable distance from the ground, which was followed by a rapid downstroke that generated more lift, launching the animal into the air.

### Locomotion

Locomotion in *Pteranodon* has historically been debated, since some used to thing its wings were used like flippers, paddling in water. However, it is most often agreed it was terrestrial and quadrupedal due to pterosaur trackways. Bennet (2001 and 1994) and Bramwell and Whitfield (1974) discuss the possibility of an aquatic Pteranodon.

### Diet

Fossil fish bones have been found in abdominal cavities and a bolus was found between the jaws of AMNH 5098. Others preserve fish scales and vertebrae associated with the torso; thus, it is assumed fish comprise most of *Pteranodon*'s diet, though it may have occasionally snacked on invertebrates. It is most often suggested to have fed to skimming while flying near-to the water's surface, which was assumed from the idea that they were unable to take flight from the water. However, the contrary is likely. It probably landed in water, snatching a few fish by dipping its beak under while swimming, and then taking flight. A small female could reach at least 80 centimeters (31 inches) in depth with the beak alone, reaching even deeper by plunge-diving from the air like most long-winged seabirds. Bennett notes the head, neck and shoulders are as heavily built as diving birds, probably diving by folding their wings like a gannet.

### Crest

Adults are separated into two size classes: small and large; large individuals are ~1.5x than the small ones, with the small being 2x as common. Historically, these have been classed as distinct, with Christopher Bennett showing their differences are consistent with males and females, that *Pteranodon* were sexually dimorphic, and that they are not distinct. The large class have large, upwards and backwards-projecting crests with the smaller class having small triangular crests. Some specimens show a second, long and low crest not observed in the smaller ones. *Pteranodon* pelvises allow for their sex to be determined. Smaller ones have a larger and wider-set pelvic region that Bennett interprets as a birth canal, with the smaller-crested individuals also representing females. The larger individuals with large crests are males.

Immature males have crests similar to mature females, making the sex of immature specimens difficult to establish. *Pteranodon* may have been polygynous since females outnumber males. They may have competed for territory on offshore rookeries with the largest, large-crested male gaining the territory and a mate. These crests would not have been used for competition. If they were for ritual, they would have had little to do with raising young, unlike modern polygynous animals.

The crests were first interpreted in 1910, where George Francis Eaton proposed they were an aerodynamic counterbalance or an anchor point for large jaw muscles; he admitted the latter would nt explain large crests. Bennet (1992) agreed with Eaton on the anchor point hypothesis, but wind tunnel tests show the crest, like Eaton had also proposed, was not an effective counterbalance, but could have been for long-crested individuals. Male *P. sternbergi* would have had a negative effect on head balance, with side-to-side movements suggesting they would have needed more musculature. Dominik von Kripp (1943) suggested it was like a rudder, which was embraced so much that Ross S. Stein even suggested it may have bore a membrane stretching to the neck and back, increasing surface area. This does not, however, take females or *P. sternbergi* into account. Bennett finds it would not have provided much directional force as using the wings. It has also been proposed it was used like a brake, where the animal could slow if it turned its head, suffers from a similar aforementioned problem. This hypothesis does not explain why such a large crest variation exists throughout the entire genus. Alexander Kellner suggests the large crests may have been used for heat exchange, which would account for the crest/body size ratio; however, no evidence of extra blood vessels required for this are known, but the wings could have served this purpose effectively given their high concentration of blood vessels. Thus, it is often concluded sexual display is the best option since crests vary intraspecies and with the established sexual dimorphism.

## Paleoecology

*Pteranodon* have been found in the Smoky Hill Chalk of the Niobrara Formation and the Sharon Springs of the Pierre Shale Formation. This area was once covered by the Western Interior Seaway, stretching from Kansas to Manitoba. However, *Pteranodon* have only been found in the southern half of the formation (Kansas, Wyoming and South Dakota), and not Canada, although many pterosaurs are known form surrounding regions. This suggests *Pteranodon* occupied a range of the southern Niobrara, not extending farther north. Some pterosaur fragments possibly attributed to *Pteranodon* are from the Gulf Coast and East Coast of the United States, but are too incomplete to identify. Some Japanese remains far from said seaway have been found, but are unlikely to be from *Pteranodon*. It was contemporaneous with *Nyctosaurus*, the latter making ~3% of pterosaurs from this formation, less common than *Ichthyornis*. It probably lived primarily on offshore rookeries based on its polygynous nature, but most fossils are found. In the seaway lived ammonites, squid, basal fish, sea turtles, plesiosaurs, diving birds, massive mosasaurs and more; "pterodactyl" (likely *Pteranodon*) bones were found in plesiosaur stomach contents. Terrestrial dinosaurs are also known from the Niobrara, suggesting their deaths happening on the coast and washing out into the sea, even showing signs of scavenging from marine fauna such as sharks.

## Classification

*Pteranodon* existed for ~4 million years, from the Early Coniacian to the Early Campanian, found in most of the Niobrara excluding the uppermost 2. *P. sternbergi* existed from 88-85 million years ago and *P. longiceps* from 86-84.5 million years ago, as found by Kenneth Carpenter (2003). Two likely chronospecies are known in a single lineage lasting 4 million years; only one species would have been present at once, with *P. sternbergi* a likely ancestor species to *P. longiceps*. Andres and Myers (2013) conclude:

## Synonyms

* *Occidentalia*
* *Geosternbergia*
* *Longicepia*
* *Dawndraco*
* *Pterodactylus oweni*
* *Pterodactylus ingens*
* *Pterodactylus occidentalis*
* *Pterodactylus velox*
* *Ornithochirus umbrosus*
* *Ornithochirus harpyia*
* *Pterodactylus umbrosus*
* *Ornithocheirus umbrosus*
* *Ornithocheirus harpyia*
* *Ornithostoma ingens*
* *Ornithostoma umbrosum*
* *Sternbergia*
* *P. (Sternbergia)*
* *P. (Geosternbergia)*

### Reassigned Species

* *P. ingens*
* *P. occidentalis*
* *P. velox*
* *P. gracilis*
* *P. comptus*
* *P. nanus*
* *P. umbrosus*
* *P. oregonensis*
* *P. marshi* (=*P. longiceps*)
* *P. bonneri*
* *P. walkeri* (=*P. longiceps*)
* *P. eatoni* (=*P. sternbergi*)
* *P. longicps* (lapsus)
* *P. orientalis*
* *P. oregonensis*

## Gallery

### Mounts

*Edmontosaurus* and *Pteranodon*.*Pteranodon* sp..*Pteranodon* sp..The private *P.* sp. "enhanced".
## References

* https://en.wikipedia.org/wiki/Pteranodon
* https://en.wikipedia.org/wiki/Eutaw\_Formation#Ornithodires
* https://twitter.com/Collinson\_C/status/1432389038619566083