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Temporal range: Late TriassicLate Cretaceous, 228–66 Ma
Pteranodon sternbergi pair.jpg
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Clade: Ornithodira
Clade: Pterosauromorpha
Padian, 1997
Order: Pterosauria
Kaup, 1834


Pterosaurs are often referred to in the popular media and by the general public as flying dinosaurs, but this is incorrect. The term "dinosaur" is restricted to just those reptiles descended from the last common ancestor of the groups Saurischia and Ornithischia (clade Dinosauria, which includes birds), and current scientific consensus is that this group excludes the pterosaurs, as well as the various groups of extinct marine reptiles, such as ichthyosaurs, plesiosaurs, and mosasaurs.[7] Like the dinosaurs, and unlike these other reptiles, pterosaurs are more closely related to birds than to crocodiles or any other living reptile. Pterosaurs are also colloquially referred to as pterodactyls, particularly by journalists.[8] Technically, "Pterodactyl" refers only to members of the genus Pterodactylus,[9] and more broadly to members of the suborder Pterodactyloidea of the pterosaurs.[10][11]




Reconstructed wing planform of Quetzalcoatlus northropi (A) compared to the wandering albatross Diomedea exulans (B) and the Andean condor Vultur gryphus (C) (not to scale)




Parts of the wing[edit]

Sordes, as depicted here, evidences the possibility that pterosaurs had a cruropatagium - a membrane connecting the legs that, unlike the chiropteran uropatagium, left the tail out.


Wing anatomy

A bone unique to pterosaurs, known as the pteroid, connected to the wrist and helped to support a forward membrane (the propatagium) between the wrist and shoulder. Evidence of webbing between the three free fingers of the pterosaur forelimb suggests that this forward membrane may have been more extensive than the simple pteroid-to-shoulder connection traditionally depicted in life restorations.[15] The position of the pteroid bone itself has been controversial. Some scientists, notably Matthew Wilkinson, have argued that the pteroid pointed forward, extending the forward membrane.[17] This view was contradicted in a 2007 paper by Chris Bennett, who showed that the pteroid did not articulate as previously thought and could not have pointed forward, but rather inward toward the body as traditionally thought.[18] Peters (2009) proposed that the pteroid articulated with the ‘saddle' of the radiale (proximal syncarpal) and both the pteroid and preaxial carpal were migrated centralia.[19] This view of the articulation of the pteroid has since been supported by specimens of Changchengopterus pani and Darwinopterus linglongtaensis, both of which show the pteroid in articulation with the proximal syncarpal.[20][21]


There has been considerable argument among paleontologists about whether the main wing membranes (brachiopatagia) attached to the hind limbs, and if so, where. Fossils of the rhamphorhynchoid Sordes,[23] the anurognathid Jeholopterus,[24] and a pterodactyloid from the Santana Formation seem to demonstrate that the wing membrane did attach to the hindlimbs, at least in some species.[25] However, modern bats and flying squirrels show considerable variation in the extent of their wing membranes and it is possible that, like these groups, different species of pterosaur had different wing designs. Indeed, analysis of pterosaur limb proportions shows that there was considerable variation, possibly reflecting a variety of wing-plans.[26]

Many, if not all, pterosaurs also had webbed feet.[27]

Skull, teeth and crests[edit]

Tooth, possibly from Coloborhynchus

Most pterosaur skulls had elongated jaws with a full complement of needle-like teeth.[28] In some cases, fossilized keratinous beak tissue has been preserved, though in toothed forms, the beak is small and restricted to the jaw tips and does not involve the teeth.[29] Some advanced beaked forms were toothless, such as the pteranodonts and azhdarchids, and had larger, more extensive, and more bird-like beaks.[28]



Some species of pterosaurs featured elaborate crests. The first and perhaps best known of these is the distinctive backward-pointing crest of some Pteranodon species, though a few pterosaurs, such as the tapejarids and Nyctosaurus, sported extremely large crests that often incorporated keratinous or other soft tissue extensions of the bony crest base.

Since the 1990s, new discoveries and more thorough study of old specimens have shown that crests are far more widespread among pterosaurs than previously thought, due mainly to the fact that they were frequently extended by or composed completely of keratin, which does not fossilize as often as bone.[15] In the case of pterosaurs like Pterorhynchus and Pterodactylus, the true extent of these crests has only been uncovered using ultraviolet photography.[29][30] The discovery of Pterorynchus and Austriadactylus, both crested "rhamphorhynchoids", showed that even primitive pterosaurs had crests (previously, crests were thought to be restricted to the more advanced pterodactyloids).[15]


At least some pterosaurs had hair-like filaments known as pycnofibers on the head and body, similar to, but not homologous (sharing a common structure) with, mammalian hair. A fuzzy integument was first reported from a specimen of Scaphognathus crassirostris in 1831 by Goldfuss,[31] and recent pterosaur finds and the technology for histological and ultraviolet examination of pterosaur specimens have provided incontrovertible proof: pterosaurs had pycnofiber coats. Pycnofibers were not true hair as seen in mammals, but a unique structure that developed a similar appearance. Although, in some cases, actinofibrils (internal structural fibers) in the wing membrane have been mistaken for pycnofibers or true hair, some fossils, such as those of Sordes pilosus (which translates as "hairy demon") and Jeholopterus ninchengensis, do show the unmistakable imprints of pycnofibers on the head and body, not unlike modern-day bats, another example of convergent evolution.[23] The head-coats do not cover the pterosaur's large jaws in many of the specimens found so far.[31]

Some (Czerkas and Ji, 2002) have speculated that pycnofibers were an antecedent of proto-feathers, but the available impressions of pterosaur integuments are not like the "quills" found on many of the bird-like maniraptoran specimens in the fossil record.[31] Pterosaur pycnofibers were structured similarly to theropod proto-feathers.[14] Pycnofibers were flexible, short filaments, "only 5-7mm in some specimens" and rather simple, "apparently lacking any internal detail aside from a central canal".[31] Pterosaur "pelts" found "preserved in concentrated, dense mats of fibers, similar to those found surrounding fossilized mammals" suggest coats with a thickness comparable to many Mesozoic mammals,[31] at least on the parts of the pterosaur covered in pycnofibers. The coat thickness, and surface area covered, definitely varied by pterosaur species, aside from pycnofibers on the wings, which have never been found.

The presence of pycnofibers (and the demands of flight) imply that pterosaurs were endothermic (warm-blooded). The absence of pycnofibers on pterosaur wings suggests that the coat did not have an aerodynamic function, lending support to the idea that pycnofibers evolved to aid pterosaur thermoregulation, as is common in warm-blooded animals, insulation being necessary to conserve the heat created by an endothermic metabolism.[31]

Pterosaur "hair" was so obviously distinct from mammalian fur and other animal integuments, it required a new, separate name. The term "pycnofiber", meaning "dense filament", was first coined in a paper on the soft tissue impressions of Jeholopterus by palaeontologist Alexander W.A. Kellner and colleagues in 2009.[14]

History of discovery[edit]


The first pterosaur fossil was described by the Italian naturalist Cosimo Alessandro Collini in 1784. Collini misinterpreted his specimen as a seagoing creature that used its long front limbs as paddles.[32] A few scientists continued to support the aquatic interpretation even until 1830, when the German zoologist Johann Georg Wagler suggested that Pterodactylus used its wings as flippers.[33] Georges Cuvier first suggested that pterosaurs were flying creatures in 1801,[34] and coined the name "Ptero-dactyle" in 1809 for the specimen recovered in Germany.[9] However, due to the standardization of scientific names, the official name for this genus became Pterodactylus, though the name "pterodactyl" continued to be popularly and incorrectly applied to all members of Pterosauria.[8] Paleontologists now avoid using "pterodactyl" and prefer the term "pterosaur". They relegate the term "pterodactyl" specifically for members of the genus Pterodactylus or more broadly for members of the suborder Pterodactyloidea.[10]




Skeletal reconstruction of a quadrupedally launching Pteranodon longiceps

The mechanics of pterosaur flight are not completely understood or modeled at this time.[35][36]


Katsufumi Sato, a Japanese scientist, did calculations using modern birds and concluded that it was impossible for a pterosaur to stay aloft.[37] In the book Posture, Locomotion, and Paleoecology of Pterosaurs it is theorized that they were able to fly due to the oxygen-rich, dense atmosphere of the Late Cretaceous period.[38] However, both Sato and the authors of Posture, Locomotion, and Paleoecology of Pterosaurs based their research on the now outdated theories of pterosaurs being seabird-like, and the size limit does not apply to terrestrial pterosaurs, such as azhdarchids and tapejarids. Furthermore, Darren Naish concluded that atmospheric differences between the present and the Mesozoic were not needed for the giant size of pterosaurs.[39]

Another issue that has been difficult to understand is how they took off. Earlier suggestions were that pterosaurs were largely cold-blooded gliding animals, deriving warmth from the environment like modern lizards, rather than burning calories. In this case, it was unclear how the enormously large giant pterosaurs, with an inefficient cold-blooded metabolism, could manage a bird-like takeoff strategy, using only the hind limbs to generate thrust for getting airborne. Later research shows them instead as being warm-blooded and having powerful flight muscles, and using the flight muscles for walking as quadrupeds.[40] Mark Witton of the University of Portsmouth and Mike Habib of Johns Hopkins University suggested that pterosaurs used a vaulting mechanism to obtain flight.[41] The tremendous power of their winged forelimbs would enable them to take off with ease.[40] Once aloft, pterosaurs could reach speeds of up to 120 kilometres per hour (75 mph) and travel thousands of kilometres.[41]



Main article: Pterosaur size

Pterosaurs had a wide range of sizes, with wingspans ranging from 250 mm (10 in) at their smallest,[42] to 10–11 m (33–36 ft) at their largest.[43]

Air sacs and respiration[edit]


Like modern crocodilians, pterosaurs appeared to have had a hepatic piston, seeing as their shoulder-pectoral girdles were too inflexible to move the sternum as in birds, and they possessed strong gastralia.[44] Thus, their respiratory system had characteristics comparable to both modern archosaur clades.

Nervous system[edit]



The flocculus sends out neural signals that produce small, automatic movements in the eye muscles. These keep the image on an animal's retina steady. Pterosaurs may have had such a large flocculus because of their large wing size, which would mean that there was a great deal more sensory information to process.[12] The low relative mass of the flocculi in birds is also a result of birds having a much larger brain overall, indicating that pterosaurs lived in a structurally simpler environment, and had less complex behaviour compared to birds.[45]

Ground movement[edit]

The probable azhdarchid trace fossil Haenamichnus uhangriensis.


There was considerable debate whether pterosaurs ambulated as quadrupeds or as bipeds. In the 1980s, paleontologist Kevin Padian suggested that smaller pterosaurs with longer hindlimbs, such as Dimorphodon, might have walked or even run bipedally, in addition to flying, like road runners.[46] However, a large number of pterosaur trackways were later found with a distinctive four-toed hind foot and three-toed front foot; these are the unmistakable prints of pterosaurs walking on all fours.[47][48]


Fossil trackways show that pterosaurs like Quetzalcoatlus northropi were quadrupeds.




Natural predators[edit]


Reproduction and life history[edit]

Fossil pterodactyloid flapling from the Solnhofen Limestone


Wing membranes preserved in pterosaur embryos are well developed, suggesting that pterosaurs were ready to fly soon after birth.[55] Fossils of pterosaurs only a few days to a week old (called "flaplings") have been found, representing several pterosaur families, including pterodactylids, rhamphorhinchids, ctenochasmatids and azhdarchids.[28] All preserve bones that show a relatively high degree of hardening (ossification) for their age, and wing proportions similar to adults. In fact, many pterosaur flaplings have been considered adults and placed in separate species in the past. Additionally, flaplings are normally found in the same sediments as adults and juveniles of the same species, such as the Pterodactylus and Rhamphorhynchus flaplings found in the Solnhofen limestone of Germany, and Pterodaustro flaplings from Brazil. All are found in deep aquatic environment far from shore.[56]



Daily activity patterns[edit]


Evolution and extinction[edit]


Restoration of two Scleromochlus on a tree

Because pterosaur anatomy has been so heavily modified for flight, and immediate transitional fossil predecessors have not so far been described, the ancestry of pterosaurs is not fully understood. Several hypotheses have been advanced, including links to theavemetatarsalian-like Scleromochlus, an ancestry among the basal archosauriforms, like Euparkeria, or among the protorosaurs.[28]



For more details on this topic, see List of pterosaur classifications.


The internal classification of pterosaurs has historically been difficult, because there were many gaps in the fossil record. Starting from the 21st Century, new discoveries are now filling in these gaps and giving a better picture of the evolution of pterosaurs. Traditionally, they were organized into two suborders: the Rhamphorhynchoidea, a "primitive" group of long-tailed pterosaurs, and the Pterodactyloidea, "advanced" pterosaurs with short tails.[28] However, this traditional division has been largely abandoned. Rhamphorhynchoidea is a paraphyletic (unnatural) group, since the pterodactyloids evolved directly from them and not from a common ancestor, so, with the increasing use of cladistics, it has fallen out of favor among most scientists.[31][64]

































The skeleton of a pterosaur on display in the Arizona Museum of Natural History in Mesa Arizona.

It was once thought that competition with early bird species might have resulted in the extinction of many of the pterosaurs.[66] By the end of the Cretaceous, only large species of pterosaurs are known. The smaller species seem to have become extinct, their niche filled by birds.[67] However, pterosaur decline (if actually present) seems unrelated to bird diversity, as ecological overlap between the two groups appears to be minimal.[68] At the end of the Cretaceous period, the Cretaceous–Paleogene extinction event, which wiped out all non-avian dinosaurs and most avian dinosaurs as well, and many other animals, seems also to have taken the pterosaurs. Alternatively, some pterosaurs may have been specialised for an ocean-going lifestyle.[citation needed] Consequently, when the Cretaceous–Paleogene extinction event severely affected marine life that these pterosaurs fed on, they went extinct. However, forms like azhdarchids and istiodactylids were not marine in habits.

In the early 2010s, several new pterosaur taxa were discovered dating to the Campanian/Maastrichtian, such as the ornithocheirids Piksi and "Ornithocheirus", possible pteranodontids and nyctosaurids, and a tapejarid.[65][69] This suggests that late Cretaceous pterosaur faunas were far more diverse than previously thought, possibly not even having declined significantly from the early Cretaceous.

It appears that pterodactyloid diversity seemingly "stalled" after the initial radiation in the Early Cretaceous, apparently not diversifying much afterwards. This would have made pterosaur diversities specialised, and thus vulnerable to minor extinction events.[70] Nonetheless, azhdarchids appear to have radiated in diversity towards the end of the Cretaceous, exploring several unusual ecological niches and increasing species wise, dismissing notions of authentic decline[71]

Small sized pterosaur species apparently were present in the Csehbánya Formation, indicating a higher diversity of Late Cretaceous pterosaurs than previously accounted for.[72]

In popular culture[edit]

Scene from Rodan (1956), a kaiju film featuring a mutated pterosaur.




In most media appearances, pterosaurs are depicted as aerial predators similar to birds of prey, grasping human victims with their taloned feet. No pterosaur species known so far possesses prehensile feet; all known pterosaurs have flat, plantigrade feet with no opposable toes, often poorly muscled and, in the case of pteranodontians, generally proportionally small.[75] However, some pterosaurs might have had raptorial tendencies; Thalassodromeus possesses powerful jaws akin to those of phorusrhacids, and Hatzegopteryx's short neck and more powerful jaws have been interpreted as a speciation on larger prey.

See also[edit]


  2. ^ Barrett, P. M., Butler, R. J., Edwards, N. P., & Milner, A. R. (2008). "Pterosaur distribution in time and space: an atlas". Zitteliana, 61-107. [1]
  14. ^ a b c Kellner, A.W.A.; Wang, X.; Tischlinger, H.; Campos, D.; Hone, D.W.E.; Meng, X. (2009). "The soft tissue of Jeholopterus (Pterosauria, Anurognathidae, Batrachognathinae) and the structure of the pterosaur wing membrane". Proceedings of the Royal Society B. doi:10.1098/rspb.2009.0846. 
  16. ^ a b Claessens LP, O'Connor PM, Unwin DM (2009). Sereno, Paul, ed. "Respiratory evolution facilitated the origin of pterosaur flight and aerial gigantism". PLoS ONE 4 (2): e4497. doi:10.1371/journal.pone.0004497. PMC 2637988. PMID 19223979. 
  19. ^ Peters D (2009). "A reinterpretation of pteroid articulation in pterosaurs.". Journal of Vertebrate Paleontology 29: 1327–1330. 
  20. ^ Zhou, Chang-Fu; Schoch, Rainer R. (2011). "New material of the non-pterodactyloid pterosaur Changchengopterus pani Lü, 2009 from the Late Jurassic Tiaojishan Formation of western Liaoning". Neues Jahrbuch für Geologie und Paläontologie–Abhandlungen 260 (3): 265–275. doi:10.1127/0077-7749/2011/0131. 
  21. ^ Wang, Xiao-Lin; Kellner, Alexander W. A.; Jiang, Shun-Xing; Cheng, Xin; Meng, Xi; Rodrigues, Taissa (2010). "New long-tailed pterosaurs (Wukongopteridae) from western Liaoning, China". Anais da Academia Brasileira de Ciências 82 (4): 1045–1062. 
  27. ^ a b c d Witton MP, Naish D (2008). McClain, Craig R., ed. "A reappraisal of azhdarchid pterosaur functional morphology and paleoecology". PLoS ONE 3 (5): e2271. doi:10.1371/journal.pone.0002271. PMC 2386974. PMID 18509539. 
  42. ^ Wang, X.; Kellner, A.W.A.; Zhou, Z.; Campos, D.A. (2008). "Discovery of a rare arboreal forest-dwelling flying reptile (Pterosauria, Pterodactyloidea) from China". Proceedings of the National Academy of Sciences 106 (6): 1983–1987. doi:10.1073/pnas.0707728105. PMC 2538868. PMID 18268340. 
  43. ^ Witton, Mark P.; Martill, David M.; Loveridge, Robert F. (2010). "Clipping the Wings of Giant Pterosaurs: Comments on Wingspan Estimations and Diversity". Acta Geoscientica Sinica 31: 79–81. 
  44. ^ Geist, N.; Hillenius, W.; Frey, E.; Jones, T.; Elgin, R. (2014). "Breathing in a box: Constraints on lung ventilation in giant pterosaurs". The Anatomical Record 297: 2233–2253. doi:10.1002/ar.22839. 
  45. ^ Hopson J.A. (1977). "Relative Brain Size and Behavior in Archosaurian Reptiles". Annual Review of Ecology and Systematics 8: 429–448. doi:10.1146/ 
  51. ^ Ji Q, Ji SA, Cheng YN et al. (December 2004). "Palaeontology: pterosaur egg with a leathery shell". Nature 432 (7017): 572. doi:10.1038/432572a. PMID 15577900. 
  53. ^ Wang, Xiaolin. "Sexually Dimorphic Tridimensionally Preserved Pterosaurs and Their Eggs from China". Current Biology. doi:10.1016/j.cub.2014.04.054. 
  61. ^ Nesbitt, S.J. (2011). "The early evolution of archosaurs: relationships and the origin of major clades" (PDF). Bulletin of the American Museum of Natural History 352: 1–292. doi:10.1206/352.1. 
  62. ^ Kellner, A. W. (2003). "Pterosaur phylogeny and comments on the evolutionary history of the group". Geological Society, London, Special Publications 217 (1): 105–137. doi:10.1144/gsl.sp.2003.217.01.10. 
  67. ^ Slack KE, Jones CM, Ando T et al. (June 2006). "Early penguin fossils, plus mitochondrial genomes, calibrate avian evolution". Mol. Biol. Evol. 23 (6): 1144–55. doi:10.1093/molbev/msj124. PMID 16533822. 
  69. ^ Agnolin, Federico L. and Varricchio, David (2012). "Systematic reinterpretation of Piksi barbarulna Varricchio, 2002 from the Two Medicine Formation (Upper Cretaceous) of Western USA (Montana) as a pterosaur rather than a bird" (PDF). Geodiversitas 34 (4): 883–894. doi:10.5252/g2012n4a10. 
  72. ^ Prondvai, E., Bodor, E. R. & Ösi, A. (2014). "Does morphology reflect osteohistology-based ontogeny? A case study of Late Cretaceous pterosaur jaw symphyses from Hungary reveals hidden taxonomic diversity". Paleobiology 40: 288–321. doi:10.1666/13030. 
  75. ^ Myths & Misconceptions

Further reading[edit]

  • Witton, Mark (2013). Pterosaurs: Natural History, Evolution, Anatomy. Princeton University Press. ISBN 978-0691150611. 

External links[edit]