Pterosaur
Overview
Pterosaurs were flying reptile
Reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...

s of the clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

 or order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 Pterosauria. They existed from the late Triassic
Triassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...

 to the end of the Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

 Period (220 to 65.5 million years ago). Pterosaurs are the earliest vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s known to have evolved powered flight. Their wings were formed by a membrane of skin, muscle, and other tissues
Tissue (biology)
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...

 stretching from the legs to a dramatically lengthened fourth finger. Early species had long, fully toothed jaws and long tails, while later forms had a highly reduced tail, and some lacked teeth.
Encyclopedia
Pterosaurs were flying reptile
Reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...

s of the clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

 or order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 Pterosauria. They existed from the late Triassic
Triassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...

 to the end of the Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

 Period (220 to 65.5 million years ago). Pterosaurs are the earliest vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s known to have evolved powered flight. Their wings were formed by a membrane of skin, muscle, and other tissues
Tissue (biology)
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...

 stretching from the legs to a dramatically lengthened fourth finger. Early species had long, fully toothed jaws and long tails, while later forms had a highly reduced tail, and some lacked teeth. Many sported furry coats made up of hair-like filaments known as pycnofibres, which covered their bodies and parts of their wings. Pterosaurs spanned a wide range of adult sizes, from the very small Nemicolopterus
Nemicolopterus
Nemicolopterus is a genus of pterodactyloid pterosaur, described in 2008. The type and only known species is N. crypticus. It lived in the Jehol Biota 120 million years ago. Its wingspan of slightly under 25 centimeters makes it smaller than any but a few specimens of hatchling...

to the largest known flying creatures of all time, including Quetzalcoatlus
Quetzalcoatlus
Quetzalcoatlus was a pterodactyloid pterosaur known from the Late Cretaceous of North America , and one of the largest known flying animals of all time. It was a member of the Azhdarchidae, a family of advanced toothless pterosaurs with unusually long, stiffened necks...

and Hatzegopteryx
Hatzegopteryx
Hatzegopteryx is a genus of azhdarchid pterosaur, known from incomplete remains found in Transylvania. The skull fragments, left humerus, and other fossilized remains indicate it was among the largest pterosaurs. The skeleton of Hatzegopteryx has been considered identical to the known remains of...

.

Pterosaurs are often referred to in the popular media and by the general public as flying dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

s, but this is incorrect. The term "dinosaur" is properly restricted to a certain group of reptiles with a unique upright stance (superorder Dinosauria, which includes bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s), and therefore excludes the pterosaurs, as well as the various groups of extinct marine reptile
Marine reptile
Marine reptiles are reptiles which have become secondarily adapted for an aquatic or semi-aquatic life in a marine environment.The earliest marine reptiles arose in the Permian period during the Paleozoic era...

s, such as ichthyosaur
Ichthyosaur
Ichthyosaurs were giant marine reptiles that resembled fish and dolphins...

s, plesiosaur
Plesiosaur
Plesiosauroidea is an extinct clade of carnivorous plesiosaur marine reptiles. Plesiosauroids, are known from the Jurassic and Cretaceous Periods...

s, and mosasaur
Mosasaur
Mosasaurs are large extinct marine lizards. The first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764...

s.

Pterosaurs are also incorrectly referred to as "pterodactyls
Pterodactyl (disambiguation)
Pterodactyl can mean:*Pterodactylus, a genus of pterosaur.*Members of the family Pterodactylidae*Members of the suborder Pterodactyloidea* Pterosaurs, an order of extinct flying reptiles...

", particularly by journalists. This usage is discouraged. "Pterodactyl" refers specifically to members of the genus Pterodactylus
Pterodactylus
Pterodactylus is a genus of pterosaurs, whose members are popularly known as pterodactyls. It was the first to be named and identified as a flying reptile...

, and more broadly to members of the suborder Pterodactyloidea
Pterodactyloidea
Pterodactyloidea forms one of the two suborders of pterosaurs , and contains the most derived members of this group of flying reptiles...

.

Description

The anatomy of pterosaurs was highly modified from their reptilian ancestors for the demands of flight. Pterosaur bones
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...

 were hollow and air-filled, like the bones of bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s. They had a keeled breastbone that was developed for the attachment of flight muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

s and an enlarged brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

 that shows specialised features associated with flight. In some later pterosaurs, the backbone over the shoulders fused into a structure known as a notarium
Notarium
Notarium is a term used for the fused vertebra of the shoulder in birds and some pterosaurs. The structure helps brace the chest against the forces generated by the wings. In birds, the vertebrae are only in contact with adjacent vertebrae and ribs, while in some pterosaurs the notarium...

, which served to stiffen the torso during flight, and provide a stable support for the scapula
Scapula
In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....

 (shoulder blade).

Wings

Pterosaur wings were formed by membranes of skin and other tissues. The primary membranes attached to the extremely long fourth finger
Finger
A finger is a limb of the human body and a type of digit, an organ of manipulation and sensation found in the hands of humans and other primates....

 of each arm
Arm
In human anatomy, the arm is the part of the upper limb between the shoulder and the elbow joints. In other animals, the term arm can also be used for analogous structures, such as one of the paired forelimbs of a four-legged animal or the arms of cephalopods...

 and extended along the sides of the body to the legs.

While historically thought of as simple, leathery structures composed of skin, research has since shown that the wing membranes of pterosaurs were actually highly complex and dynamic structures suited to an active style of flight. First, the outer wings (from the tip to the elbow) were strengthened by closely spaced fibers called actinofibrils. The actinofibrils themselves consisted of three distinct layers in the wing, forming a crisscross pattern when superimposed on one another. The actual function of the actinofibrils is unknown, as is the exact material from which they were made. Depending on their exact composition (keratin, muscle, elastic structures, etc.), they may have been stiffening or strengthening agents in the outer part of the wing. The wing membranes also contained a thin layer of muscle, fibrous tissue, and a unique, complex circulatory system of looping blood vessels.

As evidenced by hollow cavities in the wing bones of larger species and soft tissue preserved in at least one specimen, some pterosaurs extended their system of respiratory air sacs (see Paleobiology section below) into the wing membrane itself.

Parts of the pterosaur wing

The pterosaur wing membrane is divided into three basic units. The first, called the propatagium ("first membrane"), was the forward-most part of the wing and attached between the wrist and shoulder, creating the "leading edge" during flight. This membrane may have incorporated the first three fingers of the hand, as evidenced in some specimens. The brachiopatagium
Patagium
*In bats, the skin forming the surface of the wing. It is an extension of the skin of the abdomen that runs to the tip of each digit, uniting the forelimb with the body.*The patagium of a bat has four distinct parts:...

("arm membrane") was the primary component of the wing, stretching from the highly elongated fourth finger of the hand to the hind limbs (though where exactly on the hind limbs it anchored is controversial and may have varied between species, see below). Finally, at least some pterosaur groups had a membrane that stretched between the legs, possibly connecting to or incorporating the tail, called the uropatagium; the extent of this membrane isn't certain, as studies on Sordes
Sordes
Sordes was a small basal pterosaur from the Late Jurassic Karabastau Svita of Kazakhstan.The genus was named in 1971 by Aleksandr Grigorevich Sharov. The type species is Sordes pilosus. The genus name means "filth" or "scum" in Latin, a reference to evil spirits in local folklore...

seem to suggest that it simply connected the legs but did not involve the tail (rendering it a cruropatagium). It is generally agreed though that non-pterodactyloid
Rhamphorhynchoidea
The Rhamphorhynchoidea forms one of the two suborders of pterosaurs and represent an evolutionary grade of primitive members of this group of flying reptiles. This suborder is paraphyletic in relation to the Pterodactyloidea, which arose from within the Rhamphorhynchoidea, not from a more distant...

 pterosaurs had a broader uro/cruropatagium, with pterodactyloids only having membranes running along the legs; Pteranodon
Pteranodon
Pteranodon , 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...

in particular might have developed/redeveloped an uropatagium, given the structure of the tail.

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. The position of the pteroid bone itself has been controversial. Some scientists, notably David Unwin, have argued that the pteroid pointed forward, extending the forward membrane. However, this view was strongly refuted 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.

Three lines of evidence, morphological, developmental and histological, indicate that the pteroid is a true bone, rather than ossified cartilage. The origin of the pteroid is unclear: it may be a modified carpal, the first metacarpal, or a neomorph (new bone).

The pterosaur wrist consists of two inner (proximal) and four outer (distal) carpals (wrist bones), excluding the pteroid bone, which may itself be a modified distal carpal. The proximal carpals are fused together into a "syncarpal" in mature specimens, while three of the distal carpals fuse to form a distal syncarpal. The remaining distal carpal, referred to here as the medial carpal, but which has also been termed the distal lateral, or pre-axial carpal, articulates on a vertically elongate biconvex facet on the anterior surface of the distal syncarpal. The medial carpal bears a deep concave fovea that opens anteriorly, ventrally and somewhat medially, within which the pteroid articulates.

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
Sordes
Sordes was a small basal pterosaur from the Late Jurassic Karabastau Svita of Kazakhstan.The genus was named in 1971 by Aleksandr Grigorevich Sharov. The type species is Sordes pilosus. The genus name means "filth" or "scum" in Latin, a reference to evil spirits in local folklore...

, the anurognathid
Anurognathid
The Anurognathidae were a group of small pterosaurs, with short tails or tailless, that lived in Europe and Asia during the Jurassic and early Cretaceous periods...

 Jeholopterus
Jeholopterus
Jeholopterus was a small anurognathid pterosaur from the Daohugou Beds of northeastern China , between 168 and 152 million years ago), preserved with hair and skin remains.-Naming:...

, and a pterodactyloid from the Santana Formation
Santana Formation
The Santana Formation is a geologic Lagerstätte in northeastern Brazil's Araripe Basin where the states of Pernambuco, Piauí and Ceará come together. The geological formation, named after the village of Santana do Cariri, lies at the base of the Araripe Plateau...

 seem to demonstrate that the wing membrane did attach to the hindlimbs, at least in some species. However, modern bat
Bat
Bats are mammals of the order Chiroptera "hand" and pteron "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, glide rather than fly,...

s and flying squirrel
Flying squirrel
Flying squirrels, scientifically known as Pteromyini or Petauristini, are a tribe of 44 species of squirrels .- Description :...

s 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.

Many if not all pterosaurs also had webbed feet.

Skull, teeth and crests

Most pterosaur skulls had elongated, beak-like jaws. Some advanced forms were toothless (such as the pteranodonts
Pteranodontidae
The Pteranodontidae are a family of large pterosaurs of the Cretaceous Period of North America.The family was named in 1876 by Othniel Charles Marsh....

 and azhdarchids
Azhdarchidae
Azhdarchidae is a family of pterosaurs known primarily from the late Cretaceous Period, though an isolated vertebrae apparently from an azhdarchid is known from the early Cretaceous as well...

), though most sported a full complement of needle-like teeth. In some cases, actual keratin
Keratin
Keratin refers to a family of fibrous structural proteins. Keratin is the key of structural material making up the outer layer of human skin. It is also the key structural component of hair and nails...

ous 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.

Unlike most archosaur
Archosaur
Archosaurs are a group of diapsid amniotes whose living representatives consist of modern birds and crocodilians. This group also includes all extinct non-avian dinosaurs, many extinct crocodilian relatives, and pterosaurs. Archosauria, the archosaur clade, is a crown group that includes the most...

s, which have several openings in the skull in front of the eyes, in pterodactyloid pterosaurs the antorbital opening
Antorbital fenestra
An antorbital fenestra is an opening in the skull, in front of the eye sockets. This skull formation first appeared in archosaurs during the Triassic Period. Living birds today possess antorbital fenestrae, but the feature has been lost in modern crocodilians...

 and the nasal opening was merged into a single large opening, called the nasoantorbial fenestra. This likely evolved as a weight-saving feature to lighten the skull for flight.
Pterosaurs are well known for their often elaborate crests. The first and perhaps best known of these is the distinctive backward-pointing crest of some Pteranodon
Pteranodon
Pteranodon , 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...

species, though a few pterosaurs, such as the tapejarids
Tapejaridae
Tapejaridae are a family of pterodactyloid pterosaurs from the early Cretaceous period. Members are currently known from Brazil and China, where the most primitive genera are found, indicating that the family has an Asian origin....

 and Nyctosaurus
Nyctosaurus
Nyctosaurus is a genus of pterodactyloid pterosaur, the remains of which have been found in the Niobrara Formation of the mid-western United States, which, during the late Cretaceous Period, was covered in an extensive shallow sea. The genus Nyctosaurus has had numerous species referred to it,...

sported incredibly 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. In the cases of pterosaurs like Pterorhynchus
Pterorhynchus
Pterorhynchus was a genus of rhamphorhynchid "rhamphorhynchoid" pterosaur from the Late Jurassic-age Daohugou Formation of Inner Mongolia, China....

and Pterodactylus
Pterodactylus
Pterodactylus is a genus of pterosaurs, whose members are popularly known as pterodactyls. It was the first to be named and identified as a flying reptile...

, the true extent of these crests has only been uncovered using ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...

 photography. The discovery of Pterorynchus and Austriadactylus
Austriadactylus
Austriadactylus is a genus of "rhamphorhynchoid" pterosaur. The fossil remains were unearthed in Late Triassic rocks of Austria.The genus was named in 2002 by Fabio Marco Dalla Vecchia e.a.. The type species is Austriadactylus cristatus. The genus name is derived from Latin Austria and Greek...

, both crested "rhamphorhynchoids
Rhamphorhynchoidea
The Rhamphorhynchoidea forms one of the two suborders of pterosaurs and represent an evolutionary grade of primitive members of this group of flying reptiles. This suborder is paraphyletic in relation to the Pterodactyloidea, which arose from within the Rhamphorhynchoidea, not from a more distant...

", showed that even primitive pterosaurs had crests (previously, crests were thought to be restricted to the more advanced pterodactyloids
Pterodactyloidea
Pterodactyloidea forms one of the two suborders of pterosaurs , and contains the most derived members of this group of flying reptiles...

).

Pycnofibres

At least some pterosaurs were covered with hair
Hair
Hair is a filamentous biomaterial, that grows from follicles found in the dermis. Found exclusively in mammals, hair is one of the defining characteristics of the mammalian class....

-like filaments known as pycnofibres, similar to but not homologous
Homology (biology)
Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...

 (sharing a common structure) with mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

ian hair. Pycnofibres were not true hair as seen in mammals, but a unique structure that developed a similar appearance through convergent evolution
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...

. Although in some cases actinofibrils (internal structural fibres) in the wing membrane have been mistaken for pycnofibres or true hair, some fossils such as those of Sordes pilosus
Sordes
Sordes was a small basal pterosaur from the Late Jurassic Karabastau Svita of Kazakhstan.The genus was named in 1971 by Aleksandr Grigorevich Sharov. The type species is Sordes pilosus. The genus name means "filth" or "scum" in Latin, a reference to evil spirits in local folklore...

(which translates as "hairy demon") and Jeholopterus ninchengensis
Jeholopterus
Jeholopterus was a small anurognathid pterosaur from the Daohugou Beds of northeastern China , between 168 and 152 million years ago), preserved with hair and skin remains.-Naming:...

do show the unmistakable imprints of pycnofibres on the head and body, not unlike modern-day bats, another example of convergent evolution. The presence of pycnofibres (and the demands of flight) imply that pterosaurs were endotherm
Endotherm
An endotherm is an organism that produces heat through internal means, such as muscle shivering or increasing its metabolism...

ic (warm-blooded).

The term "pycnofibre", 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.

History of discovery

The first pterosaur fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

 was described by the Italian
Italian people
The Italian people are an ethnic group that share a common Italian culture, ancestry and speak the Italian language as a mother tongue. Within Italy, Italians are defined by citizenship, regardless of ancestry or country of residence , and are distinguished from people...

 naturalist Cosimo Collini in 1784. Collini misinterpreted his specimen as a seagoing creature that used its long front limbs as paddles. A few scientists continued to support the aquatic interpretation even until 1830, when the German zoologist Johann Georg Wagler
Johann Georg Wagler
Johann Georg Wagler was a German herpetologist.Wagler was assistant to Johann Baptist von Spix, and became Director of the Zoological Museum at the University of Munich after Spix's death in 1826...

 suggested that Pterodactylus used its wings as flippers. Georges Cuvier
Georges Cuvier
Georges Chrétien Léopold Dagobert Cuvier or Jean Léopold Nicolas Frédéric Cuvier , known as Georges Cuvier, was a French naturalist and zoologist...

 first suggested that pterosaurs were flying creatures in 1801, and coined the name "Ptero-dactyle" 1809 for the specimen recovered in Germany. However, due to the standardization of scientific names, the official name for this genus became Pterodactylus
Pterodactylus
Pterodactylus is a genus of pterosaurs, whose members are popularly known as pterodactyls. It was the first to be named and identified as a flying reptile...

, though the name "pterodactyl" continued to be popularly and incorrectly applied to all members of Pterosauria. 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
Pterodactyloidea
Pterodactyloidea forms one of the two suborders of pterosaurs , and contains the most derived members of this group of flying reptiles...

.

Since the first pterosaur fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

 was discovered in the Late Jurassic
Late Jurassic
The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago , which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name "Malm" indicates rocks of Late Jurassic age...

 Solnhofen limestone
Solnhofen limestone
The Solnhofen Plattenkalk is a Jurassic Konservat-Lagerstätte that preserves a rare assemblage of fossilized organisms, including highly detailed imprints of soft bodied organisms such as sea jellies...

 in 1784, twenty-nine kinds of pterosaurs have been found in those deposits alone. A famous early UK find was an example of Dimorphodon
Dimorphodon
Dimorphodon was a genus of medium-sized pterosaur from the early Jurassic Period. It was named by paleontologist Richard Owen in 1859. Dimorphodon means "two-form tooth", derived from Greek δι/di meaning 'two', μορφη/morphe meaning 'shape' and οδων/odon meaning 'tooth', referring to the fact that...

by Mary Anning
Mary Anning
Mary Anning was a British fossil collector, dealer and palaeontologist who became known around the world for a number of important finds she made in the Jurassic age marine fossil beds at Lyme Regis where she lived...

, at Lyme Regis
Lyme Regis
Lyme Regis is a coastal town in West Dorset, England, situated 25 miles west of Dorchester and east of Exeter. The town lies in Lyme Bay, on the English Channel coast at the Dorset-Devon border...

 in 1828. The name Pterosauria was coined by Johann Jakob Kaup
Johann Jakob Kaup
Johann Jakob Kaup was a German naturalist.-Biography:He was born at Darmstadt. After studying at Göttingen and Heidelberg he spent two years at Leiden, where his attention was specially devoted to the amphibians and fishes. He then returned to Darmstadt as an assistant in the grand ducal museum,...

 in 1834, though the name Ornithosauria (or "bird lizards", Bonaparte, 1838) was sometimes used in the early literature.http://www.fmnh.helsinki.fi/users/haaramo/Metazoa/Deuterostoma/Chordata/Archosauria/Pterosauria/Pterosauria_4.html
Most pterosaur fossils are poorly preserved. Their bone
Bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...

s were hollow and, when sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....

s piled on top of them, the bones were flattened. The best preserved fossils have come from the Araripe Plateau, Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

. For some reason, when the bones were deposited, the sediments encapsulated the bones, rather than crushing them. This created three-dimensional fossils for paleontologists to study. The first find in the Araripe Plateau was made in 1974.

Most paleontologists now believe that pterosaurs were adapted for active flight
Flight
Flight is the process by which an object moves either through an atmosphere or beyond it by generating lift or propulsive thrust, or aerostatically using buoyancy, or by simple ballistic movement....

, not just gliding
Gliding
Gliding is a recreational activity and competitive air sport in which pilots fly unpowered aircraft known as gliders or sailplanes using naturally occurring currents of rising air in the atmosphere to remain airborne. The word soaring is also used for the sport.Gliding as a sport began in the 1920s...

 as was earlier believed. Pterosaur fossils have been found on every continent. At least 60 genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of pterosaurs have been found to date, ranging from the size of a small bird to wingspans in excess of 10 metres (33 ft).

Flight

The mechanics of pterosaur flight are not completely understood or modeled at this time.

Katsufumi Sato, a Japanese scientist, did calculations using modern birds and decided that it is impossible for a pterosaur to stay aloft. 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
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...

 period. However, one must note both Katsufumi 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 doesn't apply to terrestrial pterosaurs like azhdarchids
Azhdarchidae
Azhdarchidae is a family of pterosaurs known primarily from the late Cretaceous Period, though an isolated vertebrae apparently from an azhdarchid is known from the early Cretaceous as well...

 and tapejarids
Tapejaridae
Tapejaridae are a family of pterodactyloid pterosaurs from the early Cretaceous period. Members are currently known from Brazil and China, where the most primitive genera are found, indicating that the family has an Asian origin....

 http://www.flickr.com/photos/markwitton/2964871173/in/set-72057594082038974/ Furthermore, Darren Naish
Darren Naish
Darren Naish is a vertebrate palaeontologist and science writer. He obtained a geology degree at the University of Southampton and later studied vertebrate palaeontology under British palaeontologist David Martill at the University of Portsmouth, where he obtained both an M. Phil...

 concluded that atmospheric differences between the present and the Mesozoic weren't needed for the giant size of pterosaurs.

However, Mark Witton and Mike Habib, of the University of Portsmouth and Johns Hopkins University, respectively, argue that pterosaurs used a vaulting mechanism to obtain flight. Once in air, pterosaurs could reach speeds up to 120 kilometres per hour (74.6 mph) and travel thousands of kilometres.

It may be of relevance that in 1985 the Smithsonian Institution commissioned aeronautical engineer Paul MacCready
Paul MacCready
Paul B. MacCready, Jr. was an American aeronautical engineer. He was the founder of AeroVironment and the designer of the human-powered aircraft that won the Kremer prize...

 to build a half-scale working model of Quetzalcoatlus northropi. The replica was launched with a ground-based winch. It flew several times in 1986 and was filmed as part of the Smithsonian's IMAX film On the Wing. However, the model was not anatomically correct and embodied vertical and horizontal tail stabilizers that were lacking in pterosaurs. The weight distribution of the model was also different due to the longer tail of the model.

Air sacs and respiration

A 2009 study showed that pterosaurs had a lung-air sac system and a precisely controlled skeletal breathing pump, which supports a flow-through pulmonary ventilation model in pterosaurs, analogous to that of birds. The presence of a subcutaneous air sac system in at least some pterodactyloids would have further reduced the density of the living animal.

Nervous system

A study of pterosaur brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

 cavities using X-rays revealed that the animals (Rhamphorhynchus muensteri and Anhanguera
Anhanguera (pterosaur)
Anhanguera is a genus of pterodactyloid pterosaur known from the Lower-Cretaceous Santana Formation of Brazil, with referred specimens found in the Upper Chalk Formation and Cambridge Greensand of the UK...

 santanae
) had massive flocculi. The flocculus is a brain region that integrates signals from joints, muscles, skin and balance organs.

The pterosaurs' flocculi occupied 7.5% of the animals' total brain mass, more than in any other vertebrate. Birds have unusually large flocculi compared with other animals, but these only occupy between 1 and 2% of total brain mass.

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.

Ground movement

Pterosaur's hip sockets are oriented facing slightly upwards, and the head of the femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...

 (thigh bone) is only moderately inward facing, suggesting that pterosaurs had a semi-erect stance. It would have been possible to lift the thigh into a horizontal position during flight as gliding lizards do.

There was considerable debate whether pterosaurs ambulated as quadruped
Quadruped
Quadrupedalism is a form of land animal locomotion using four limbs or legs. An animal or machine that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet"...

s or as biped
Biped
Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs, or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning "two feet"...

s. In the 1980s, paleontologist Kevin Padian
Kevin Padian
Kevin Padian is a Professor of Integrative Biology at the University of California, Berkeley, Curator of Paleontology, University of California Museum of Paleontology and President of the National Center for Science Education. Padian's area of interest is in vertebrate evolution, especially the...

 suggested that smaller pterosaurs with longer hindlimbs such as Dimorphodon
Dimorphodon
Dimorphodon was a genus of medium-sized pterosaur from the early Jurassic Period. It was named by paleontologist Richard Owen in 1859. Dimorphodon means "two-form tooth", derived from Greek δι/di meaning 'two', μορφη/morphe meaning 'shape' and οδων/odon meaning 'tooth', referring to the fact that...

might have walked or even run bipedally, in addition to flying, like road runners
Geococcyx
The roadrunners are two species of bird in the genus Geococcyx of the cuckoo family, Cuculidae, native to North and Central America...

. However, a large number of pterosaur trackways
Fossil trackway
A fossil trackway is a type of trace fossil, a trackway made by an organism. Many fossil trackways were made by dinosaurs, early tetrapods, and other quadrupeds and bipeds on land...

 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.

Unlike most vertebrates, which walk on their toes with ankles held off the ground (digitigrade
Digitigrade
A digitigrade is an animal that stands or walks on its digits, or toes. Digitigrades include walking birds , cats, dogs, and many other mammals, but not plantigrades or unguligrades...

), fossil footprints show that pterosaurs stood with the entire foot in contact with the ground (plantigrade
Plantigrade
right|151px|thumb|Human skeleton, showing plantigrade habitIn terrestrial animals, plantigrade locomotion means walking with the podials and metatarsals flat on the ground. It is one of three forms of locomotion adopted by mammals...

), in a manner similar to human
Human
Humans are the only living species in the Homo genus...

s and bear
Bear
Bears are mammals of the family Ursidae. Bears are classified as caniforms, or doglike carnivorans, with the pinnipeds being their closest living relatives. Although there are only eight living species of bear, they are widespread, appearing in a wide variety of habitats throughout the Northern...

s. Footprints from azhdarchids
Azhdarchidae
Azhdarchidae is a family of pterosaurs known primarily from the late Cretaceous Period, though an isolated vertebrae apparently from an azhdarchid is known from the early Cretaceous as well...

 show that at least some pterosaurs walked with an erect, rather than sprawling, posture.
Though traditionally depicted as ungainly and awkward when on the ground, the anatomy of at least some pterosaurs (particularly pterodactyloids) suggests that they were competent walkers and runners. The forelimb bones of azhdarchids
Azhdarchidae
Azhdarchidae is a family of pterosaurs known primarily from the late Cretaceous Period, though an isolated vertebrae apparently from an azhdarchid is known from the early Cretaceous as well...

 and ornithocheirids
Ornithocheiridae
Ornithocheiridae is a group of pterosaurs within the suborder Pterodactyloidea. They were among the last pterosaurs to possess teeth.-Classification:Listing of genera after Unwin , except where noted.* Family Ornithocheiridae** ?Aetodactylus...

 were unusually long compared to other pterosaurs, and in azhdarchids, the bones of the arm and hand (metacarpals) were particularly elongated. Furthermore, azhdarchid front limbs as a whole were proportioned similarly to fast-running ungulate
Ungulate
Ungulates are several groups of mammals, most of which use the tips of their toes, usually hoofed, to sustain their whole body weight while moving. They make up several orders of mammals, of which six to eight survive...

 mammals. Their hind limbs, on the other hand, were not built for speed, but they were long compared with most pterosaurs, and allowed for a long stride length. While azhdarchid pterosaurs probably could not run, they would have been relatively fast and energy efficient.

The relative size of the hands and feet in pterosaurs (by comparison with modern animals such as birds) may indicate what type of lifestyle pterosaurs led on the ground. Azhdarchid pterosaurs had relatively small feet compared to their body size and leg length, with foot length only about 25%-30% the length of the lower leg. This suggests that azhdarchids were better adapted to walking on dry, relatively solid ground. Pteranodon
Pteranodon
Pteranodon , 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...

had slightly larger feet (47% the length of the tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....

), while filter-feeding pterosaurs like the ctenochasmatoids
Ctenochasmatoidea
Ctenochasmatoidea is a group of pterosaurs within the suborder Pterodactyloidea.-Classification:Cladogram after Unwin ....

 had very large feet (69% of tibial length in Pterodactylus
Pterodactylus
Pterodactylus is a genus of pterosaurs, whose members are popularly known as pterodactyls. It was the first to be named and identified as a flying reptile...

, 84% in Pterodaustro
Pterodaustro
Pterodaustro is a genus of Cretaceous pterodactyloid pterosaur from South America, which lived 105 million years ago.-Naming:The genus was named in 1969 by José Bonaparte as an as yet undescribed nomen nudum. The first description followed in 1970, making the name valid, the type species being...

), adapted to walking in soft muddy soil, similar to modern wading birds.

Natural predators

Pterosaurs are known to have been eaten by theropods
Theropoda
Theropoda is both a suborder of bipedal saurischian dinosaurs, and a clade consisting of that suborder and its descendants . Dinosaurs belonging to the suborder theropoda were primarily carnivorous, although a number of theropod groups evolved herbivory, omnivory, and insectivory...

. In the 1 July 2004 edition of Nature
Nature (journal)
Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...

, paleontologist Eric Buffetaut discusses an early Cretaceous fossil of three cervical vertebrae of a pterosaur with the broken tooth of a spinosaur embedded in it. The vertebrae are known not to have been eaten and exposed to digestion, as the joints still articulated.

Reproduction and life history

Very little is known about pterosaur reproduction, and pterosaur eggs are very rare. The first known pterosaur egg was found in the quarries of Liaoning, the same place that yielded the famous 'feathered' dinosaurs. The egg was squashed flat with no signs of cracking, so evidently the eggs had leathery shells, as in modern lizards. This was supported by the description of an additional pterosaur egg belonging to the genus Darwinopterus
Darwinopterus
Darwinopterus is a genus of pterosaur, discovered in China and named after biologist Charles Darwin. Between 30 and 40 fossil specimens have been identified, all collected from the Tiaojishan Formation, which dates to the middle Jurassic period. The type species, D. modularis, was described in...

, described in 2011, which also had a leathery shell and, also like modern reptiles but unlike birds, was fairly small compared to the size of the mother. A study of pterosaur eggshell structure and chemistry published in 2007 indicated that it is likely pterosaurs buried their eggs, like modern crocodile
Crocodile
A crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all extant members of the order Crocodilia: i.e...

s and turtle
Turtle
Turtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield...

s. Egg-burying would have been beneficial to the early evolution of pterosaurs, as it allows for more weight-reducing adaptations, but this method of reproduction also would have put limits on the variety of environments pterosaurs could live in, and may have disadvantaged them when they began to face ecological competition from bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s.

Wing membranes preserved in pterosaur embryos are well developed, suggesting pterosaurs were ready to fly soon after birth. 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. All preserve bones which 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
Solnhofen limestone
The Solnhofen Plattenkalk is a Jurassic Konservat-Lagerstätte that preserves a rare assemblage of fossilized organisms, including highly detailed imprints of soft bodied organisms such as sea jellies...

 of Germany, and Pterodaustro flaplings from Brazil. All are found in deep aquatic environment far from shore.

It is not known whether pterosaurs practiced any form of parental care, but their ability to fly as soon as they emerged from the egg and the numerous flaplings found in environments far from nests and alongside adults has led most researchers, including Christopher Bennett and David Unwin, to conclude that the young were only dependent on their parents for a very short period of time, while the wings grew long enough to fly, and left the nest to fend for themselves within days of hatching. Alternatively, they may have used stored yolk products for nourishment during their first few days of life, as in modern reptiles, rather than depend on parents for food.

Growth rates of pterosaurs once they hatched varied across different groups. In more primitive, long-tailed pterosaurs ("rhamphorhynchoids") such as Rhamphorhynchus, the average growth rate during the first year of life was 130% to 173%, slightly faster than the growth rate of alligator
Alligator
An alligator is a crocodilian in the genus Alligator of the family Alligatoridae. There are two extant alligator species: the American alligator and the Chinese alligator ....

s. Growth in these species slowed after sexual maturity, and it would have taken more than three years for Rhamphorhynchus to attain maximum size. In contrast, the more advanced, large pterodactyloid pterosaurs such as Pteranodon
Pteranodon
Pteranodon , 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...

grew to adult size within the first year of life. Additionally, pterodactyloids had determinate growth, meaning that the animals reached a fixed maximum adult size and stopped growing.

Daily activity patterns

Comparisons between the scleral ring
Sclerotic ring
Sclerotic rings are rings of bone found in the eyes of several groups of vertebrate animals, except for mammals and crocodilians. They can be made up of single bones or small bones together. They are believed to have a role in supporting the eye, especially in animals whose eyes are not spherical,...

s of pterosaurs and modern birds and reptiles have been used to infer daily activity patterns of pterosaurs. The pterosaur genera Pterodactylus
Pterodactylus
Pterodactylus is a genus of pterosaurs, whose members are popularly known as pterodactyls. It was the first to be named and identified as a flying reptile...

, Scaphognathus
Scaphognathus
Scaphognathus was a pterosaur that lived around Germany during the Late Jurassic. It had a wingspan of about one meter.-Naming:The first known Scaphognathus specimen was described in 1831 by August Goldfuss who mistook the tailless specimen for a new Pterodactylus species: P. crassirostris. The...

, and Tupuxuara
Tupuxuara
Tupuxuara is a genus of large, crested, toothless pterodactyloid pterosaur.The genus was in 1988 named and described by Alexander Kellner and Diogenes de Almeida Campos. The type species is Tupuxuara longicristatus. The genus name refers to a familiar spirit from the mythology of the Tupi...

have been inferred to be diurnal, Ctenochasma
Ctenochasma
Ctenochasma is a genus of Late Jurassic pterosaur belonging to the suborder pterodactyloidea. Three species are currently recognized: C. roemeri , C. taqueti, and C. elegans...

, Pterodaustro
Pterodaustro
Pterodaustro is a genus of Cretaceous pterodactyloid pterosaur from South America, which lived 105 million years ago.-Naming:The genus was named in 1969 by José Bonaparte as an as yet undescribed nomen nudum. The first description followed in 1970, making the name valid, the type species being...

, and Rhamphorhynchus
Rhamphorhynchus
Rhamphorynchus may refer to:*Rhamphorhynchus, a genus of pterosaur*Rhamphorhynchus, a former monotypic genus of orchid, containing only the species now called Aspidogyne mendoncae...

have been inferred to be nocturnal, and Tapejara has been inferred to be cathemeral
Cathemeral
A cathemeral organism is one that has sporadic and random intervals of activity during the day or night in which food is acquired, socializing with other organisms occurs, and any other activities necessary for livelihood are performed...

, being active throughout the day for short intervals. As a result, the possibly fish-eating Ctenochasma and Rhamphorhynchus may have had similar activity patterns to modern nocturnal seabirds, and the filter-feeding Pterodaustro may have had similar activity patterns to modern anseriform
Anseriformes
The order Anseriformes contains about 150 living species of birds in three extant families: the Anhimidae , Anseranatidae , and the Anatidae, which includes over 140 species of waterfowl, among them the ducks, geese, and swans.All species in the order are highly adapted for an aquatic existence at...

 birds that feed at night. The differences between activity patterns of the Solnhofen
Paleobiota of the Solnhofen Formation
-Chondrostei:-Semionotidae:-Macrosemiidae:-Pycnodontiformes:-Pachycormidae:-Others:-Caturidae:-Ionoscopidae:-Furidae:-Other halecomorphs:-Halecomorphi incertae cedis:-Pleuropholidae:-Aspidorhynchidae:-Pholidophoridae:...

 pterosaurs Ctenochasma, Rhamphorhynchus, Scaphognathus, and Pterodactylus may also indicate niche partitioning between these genera.

Origins

Because pterosaur anatomy
Anatomy
Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant anatomy...

 has been so heavily modified for flight, and immediate "missing link" predecessors have not so far been described, the ancestry of pterosaurs is not well understood. Several hypotheses have been advanced, including links to ornithodirans like Scleromochlus
Scleromochlus
Scleromochlus is an extinct genus of small avemetatarsalian from the Late Triassic period. A lightly built cursorial animal, its phylogenetic position has been debated; as different analyses have found it to be either the basal-most ornithodiran, the sister-taxon to Pterosauria, or a basal member...

, an ancestry among the basal archosauriforms
Archosauriformes
Archosauriformes is a clade of diapsid reptiles that developed from archosauromorph ancestors some time in the Late Permian...

 like Euparkeria
Euparkeria
Euparkeria was a small African reptile of the early Triassic period between 248-245 million years ago, close to the ancestry of the archosaurs.- Palaeobiology :...

, or among the prolacertiformes
Prolacertiformes
Prolacertiformes were an order of archosauromorph reptiles that lived during the Permian and Triassic Periods...

 (which include gliding forms like Sharovipteryx
Sharovipteryx
Sharovipteryx , was an early gliding reptile, from the middle-late Triassic period . Fossils have been found from the Madygen Formation of Kyrgyzstan along with the unusual reptile Longisquama...

).

Two researchers, Chris Bennett
Chris Bennett
Chris Bennett may refer to:* Chris Bennett , Grammy-nominated singer, dancer and composer* Chris Bennett , former Canadian international and NASL soccer player...

 (1996) and David Peters (2000), have found pterosaurs to be prolacertiformes or closely related to them. Bennett only recovered pterosaurs as close relatives of the prolacertiformes after removing characteristics of the hind limb from his analysis, in an attempt to test the idea that these characters are the result of convergent evolution
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...

 between pterosaurs and dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

s. However, subsequent analysis by Dave Hone and Michael Benton (2007) could not reproduce this result. Hone and Benton found pterosaurs to be closely related to dinosaurs even without hind limb characters. They also criticized previous studies by David Peters, raising "serious questions" about the methods he used to recover pterosaurs among the prolacertiformes. Hone and Benton concluded that although more primitive pterosauromorphs are needed to clarify their relationships, pterosaurs are best considered archosaurs, and specifically ornithodirans, given current evidence. In Hone and Benton's analysis, pterosaurs are either the sister group of Scleromochlus or fall between it and Lagosuchus
Lagosuchus
Lagosuchus is a genus of small archosaur from the middle Triassic period. It is generally thought to be closely related to dinosaurs, as a member of the Dinosauromorpha...

on the ornithodiran family tree. Sterling Nesbitt
Sterling Nesbitt
Sterling Nesbitt , is an American paleontologist.-Biography:Sterling Nesbitt received his B.A. in integrative biology with a minor in geology from University of California Berkeley in 2004. He received his Ph.D from Columbia University in 2009, completing the majority of his research at the...

 (2011) found strong support for a clade composed of Scleromochlus and pterosaurs.

Classification

Classification
Biological classification
Biological classification, or scientific classification in biology, is a method to group and categorize organisms by biological type, such as genus or species. Biological classification is part of scientific taxonomy....

 of pterosaurs has historically been difficult, because there were many gaps in the fossil record. Many new discoveries are now filling in these gaps and giving a better picture of the evolution of pterosaurs. Traditionally, they are organized into two suborders:
  • Rhamphorhynchoidea
    Rhamphorhynchoidea
    The Rhamphorhynchoidea forms one of the two suborders of pterosaurs and represent an evolutionary grade of primitive members of this group of flying reptiles. This suborder is paraphyletic in relation to the Pterodactyloidea, which arose from within the Rhamphorhynchoidea, not from a more distant...

     (Plieninger, 1901): A group of early, basal ("primitive") pterosaurs, many of which had long tails and short metacarpal bones in the wing. They were small, and their fingers were still adapted to climbing . They appeared in the Late Triassic period, and lasted until the late Jurassic. Rhamphorhynchoidea is a paraphyletic group (since the pterodactyloids evolved directly from them and not from a common ancestor), so with the increasing use of cladistics
    Cladistics
    Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...

     it has fallen out of favor in most technical literature.

  • Pterodactyloidea
    Pterodactyloidea
    Pterodactyloidea forms one of the two suborders of pterosaurs , and contains the most derived members of this group of flying reptiles...

     (Plieninger, 1901): The more derived ("advanced") pterosaurs, with short tails and long wing metacarpals. They appeared in the middle Jurassic
    Jurassic
    The Jurassic is a geologic period and system that extends from about Mya to  Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...

     period, and lasted until the Cretaceous-Tertiary extinction event
    Cretaceous-Tertiary extinction event
    The Cretaceous–Paleogene extinction event, formerly named and still commonly referred to as the Cretaceous-Tertiary extinction event, occurred approximately 65.5 million years ago at the end of the Maastrichtian age of the Cretaceous period. It was a large-scale mass extinction of animal and plant...

     wiped them out at the end of the Cretaceous
    Cretaceous
    The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

    .


Listing of families and superfamilies within Pterosauria, after Unwin 2006 unless otherwise noted.
  • ORDER PTEROSAURIA (extinct)
    • Suborder Rhamphorhynchoidea
      Rhamphorhynchoidea
      The Rhamphorhynchoidea forms one of the two suborders of pterosaurs and represent an evolutionary grade of primitive members of this group of flying reptiles. This suborder is paraphyletic in relation to the Pterodactyloidea, which arose from within the Rhamphorhynchoidea, not from a more distant...

      *
      • Family Anurognathidae
      • Family Campylognathoididae
        Campylognathoididae
        Campylognathoididae is a group of early "rhamphorhynchoid" pterosaurs named after Campylognathoides, that lived in the Late Jurassic. The family Campylognathoididae was named in 1967 by Oskar Kuhn, originally as the subfamily Campylognathoidinae....

      • Family Dimorphodontidae
        Dimorphodontidae
        Dimorphodontidae is a family of early "rhamphorhynchoid" pterosaurs named after Dimorphodon, that lived in the Late Triassic to Early Jurassic....

      • Family Rhamphorhynchidae
        Rhamphorhynchidae
        Rhamphorhynchidae is a group of early "rhamphorhynchoid" pterosaurs named after Rhamphorhynchus, that lived in the Late Jurassic. The family Rhamphorhynchidae was named in 1870 by Harry Govier Seeley.-Classification:...

    • Suborder Pterodactyloidea
      Pterodactyloidea
      Pterodactyloidea forms one of the two suborders of pterosaurs , and contains the most derived members of this group of flying reptiles...

      • Superfamily Ornithocheiroidea
        Ornithocheiroidea
        Ornithocheiroidea is an extinct group of pterosaurs within the suborder Pterodactyloidea.-Locomotion:Ornithocheiroids, like other pterosaurs, are considered to have been skilled fliers as well as adept at moving on the ground...

        • Family Istiodactylidae
          Istiodactylidae
          Istiodactylidae is a small family of pterosaurs. This family was named in 2001 after the type genus Istiodactylus was discovered not to be a member of the genus Ornithodesmus....

        • Family Nyctosauridae
          Nyctosauridae
          Nyctosauridae is a family of specialized soaring pterosaurs of the Cretaceous Period of North America and, possibly, Europe. It was named in 1889 by Henry Alleyne Nicholson and Richard Lydekker....

        • Family Ornithocheiridae
          Ornithocheiridae
          Ornithocheiridae is a group of pterosaurs within the suborder Pterodactyloidea. They were among the last pterosaurs to possess teeth.-Classification:Listing of genera after Unwin , except where noted.* Family Ornithocheiridae** ?Aetodactylus...

        • Family Pteranodontidae
          Pteranodontidae
          The Pteranodontidae are a family of large pterosaurs of the Cretaceous Period of North America.The family was named in 1876 by Othniel Charles Marsh....

      • Superfamily Ctenochasmatoidea
        Ctenochasmatoidea
        Ctenochasmatoidea is a group of pterosaurs within the suborder Pterodactyloidea.-Classification:Cladogram after Unwin ....

        • Family Ctenochasmatidae
          Ctenochasmatidae
          Ctenochasmatidae is a group of pterosaurs within the suborder Pterodactyloidea.-Classification:Listing of subfamilies and genera after Unwin 2006 unless otherwise noted.* Family Ctenochasmatidae** Elanodactylus** Gegepterus...

        • Family Gallodactylidae
          Gallodactylidae
          Gallodactylidae is a group of pterosaurs within the suborder Pterodactyloidea....

        • Family Pterodactylidae
      • Superfamily Dsungaripteroidea
        Dsungaripteroidea
        Dsungaripteroidea is a group of pterosaurs within the suborder Pterodactyloidea.-Classification:Listing of families and genera after Unwin 2006 unless otherwise noted.* Superfamily Dsungaripteroidea** Herbstosaurus** Kepodactylus...

        • Family Dsungaripteridae
          Dsungaripteridae
          Dsungaripteridae is a group of pterosaurs within the suborder Pterodactyloidea....

        • Family Germanodactylidae
          Germanodactylidae
          Germanodactylidae is a group of pterosaurs within the suborder Pterodactyloidea. While its exact placement and content are controversial, recent studies have suggested it contains three genera: Germanodactylus, Normannognathus and Tendaguripterus...

      • Superfamily Azhdarchoidea
        Azhdarchoidea
        Azhdarchoidea is a group of pterosaurs within the suborder Pterodactyloidea.-Classification:Listing of families and genera after Unwin 2006 except where specified.* Superfamily Azhdarchoidea** Genus "Aurorazhdarcho"** Family Chaoyangopteridae...

        • Family Azhdarchidae
          Azhdarchidae
          Azhdarchidae is a family of pterosaurs known primarily from the late Cretaceous Period, though an isolated vertebrae apparently from an azhdarchid is known from the early Cretaceous as well...

        • Family Chaoyangopteridae
          Chaoyangopteridae
          The Chaoyangopteridae are a family of pterosaurs within the Azhdarchoidea.The clade Chaoyangopteridae was first defined in 2008 by Lü Junchang and David Unwin as: "Chaoyangopterus, Shenzhoupterus, their most recent common ancestor and all taxa more closely related to this clade than to Tapejara,...

        • Family Lonchodectidae
        • Family Tapejaridae
          Tapejaridae
          Tapejaridae are a family of pterodactyloid pterosaurs from the early Cretaceous period. Members are currently known from Brazil and China, where the most primitive genera are found, indicating that the family has an Asian origin....



The precise relationships between pterosaurs is still unsettled. However, several newer studies are beginning to make things clearer. Cladogram
Cladogram
A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...

 simplified after Unwin.

Extinction

It was once thought that competition with early bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

 species may have resulted in the extinction of many of the pterosaurs. 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. However, pterosaur decline (if actually present) seems unrelated to bird diversity. At the end of the Cretaceous period, the Cretaceous–Tertiary extinction event which wiped out all non-avian dinosaurs and most avian dinosaurs as well, and many other animals, seemed to also take the pterosaurs. Alternatively, most pterosaurs may have been specialised for an ocean-going lifestyle. Consequently, when the Cretaceous–Tertiary extinction event severely affected marine life that most pterosaurs fed on, they went extinct. However, forms like azhdarchids
Azhdarchidae
Azhdarchidae is a family of pterosaurs known primarily from the late Cretaceous Period, though an isolated vertebrae apparently from an azhdarchid is known from the early Cretaceous as well...

 and istiodactylids
Istiodactylus
Istiodactylus was a medium sized pterosaur from the Early Cretaceous period.-History and species:In 1887 Harry Govier Seeley named the remains of a fossil pelvis discovered on the Isle of Wight, Ornithodesmus cluniculus, thinking it was a bird. In 1901 he considered that it might have been a...

 were not marine in habits.

Well-known genera

Examples of pterosaur genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 include:
  • Pteranodon
    Pteranodon
    Pteranodon , 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...

    was 1.8 metres (six ft) long, with a wingspan of 7.5 m (25 ft), and lived during the late Cretaceous period.
  • Pterodactylus
    Pterodactylus
    Pterodactylus is a genus of pterosaurs, whose members are popularly known as pterodactyls. It was the first to be named and identified as a flying reptile...

    had a wingspan of 50–75 centimetres (20 to –30 inches), and lived during the late Jurassic on lake
    Lake
    A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

     shores.
  • Pterodaustro
    Pterodaustro
    Pterodaustro is a genus of Cretaceous pterodactyloid pterosaur from South America, which lived 105 million years ago.-Naming:The genus was named in 1969 by José Bonaparte as an as yet undescribed nomen nudum. The first description followed in 1970, making the name valid, the type species being...

    was a Cretaceous pterosaur from South America
    South America
    South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

     with a wingspan around 1.33 metres and with over 500 tall, narrow teeth, which were presumably used in filter-feeding, much like modern flamingo
    Flamingo
    Flamingos or flamingoes are gregarious wading birds in the genus Phoenicopterus , the only genus in the family Phoenicopteridae...

    s. Also like flamingos, this pterosaur's diet may have resulted in the animal having a pink
    Pink
    Pink is a mixture of red and white. Commonly used for Valentine's Day and Easter, pink is sometimes referred to as "the color of love." The use of the word for the color known today as pink was first recorded in the late 17th century....

     hue. It was South America's first pterosaur find.
  • Quetzalcoatlus
    Quetzalcoatlus
    Quetzalcoatlus was a pterodactyloid pterosaur known from the Late Cretaceous of North America , and one of the largest known flying animals of all time. It was a member of the Azhdarchidae, a family of advanced toothless pterosaurs with unusually long, stiffened necks...

    had a wingspan of 10–11 metres (33–36 ft), and was among the largest flying animals ever. It lived during the late Cretaceous period.
  • Hatzegopteryx
    Hatzegopteryx
    Hatzegopteryx is a genus of azhdarchid pterosaur, known from incomplete remains found in Transylvania. The skull fragments, left humerus, and other fossilized remains indicate it was among the largest pterosaurs. The skeleton of Hatzegopteryx has been considered identical to the known remains of...

    was the largest flying animal known to science. Although no complete fossil has been discovered, what little fossils paleontologists
    Paleontology
    Paleontology "old, ancient", ὄν, ὀντ- "being, creature", and λόγος "speech, thought") is the study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments...

     have found give the creature an estimated wingspan of roughly 12 metres (40 ft.)
  • Rhamphorhynchus
    Rhamphorhynchus (animal)
    Rhamphorhynchus , "beak snout", is a genus of long-tailed pterosaurs in the Jurassic period. Less specialized than contemporary, short-tailed pterodactyloid pterosaurs such as Pterodactylus, it had a long tail, stiffened with ligaments, which ended in a characteristic diamond-shaped vane...

    was a Jurassic pterosaur with a vane at the end of its tail, which may have acted to stabilise the tail in flight.

In popular culture

Pterosaurs have been a staple of popular culture for as long as their cousins the dinosaurs, though they are usually not featured as prominently in films, literature or other art. Additionally, while the depiction of dinosaurs in popular media has changed radically in response to advances in paleontology, a mainly outdated picture of pterosaurs has persisted since the mid 20th century.

The number and diversity of pterosaurs in the popular consciousness is also not as high as it has been historically for dinosaurs. While the generic term "pterodactyl" is often used to describe these creatures, the animals depicted frequently represent either Pteranodon
Pteranodon
Pteranodon , 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...

or Rhamphorhynchus
Rhamphorhynchus (animal)
Rhamphorhynchus , "beak snout", is a genus of long-tailed pterosaurs in the Jurassic period. Less specialized than contemporary, short-tailed pterodactyloid pterosaurs such as Pterodactylus, it had a long tail, stiffened with ligaments, which ended in a characteristic diamond-shaped vane...

, or a fictionalized hybrid of the two. Many children's toys and cartoons feature "pterodactyls" with Pteranodon-like crests and long, Rhamphorhynchus
Rhamphorhynchus (animal)
Rhamphorhynchus , "beak snout", is a genus of long-tailed pterosaurs in the Jurassic period. Less specialized than contemporary, short-tailed pterodactyloid pterosaurs such as Pterodactylus, it had a long tail, stiffened with ligaments, which ended in a characteristic diamond-shaped vane...

-like tails and teeth, a combination that never existed in nature. However, at least one type of pterosaur did have at least the Pteranodon-like crest and teeth—for example, the Ludodactylus
Ludodactylus
Ludodactylus was a genus of ornithocheirid pterodactyloid pterosaur from the Aptian-age Lower Cretaceous Crato Formation of Ceará, Brazil....

, a name that means "toy finger" for its resemblance to old, inaccurate children's toys. Also, some depictions of pterosaurs incorrectly identify them as "birds", when in real life they were flying reptiles, and birds are actually descended from theropod dinosaurs.

Pterosaurs were first used in fiction in Arthur Conan Doyle's 1912 novel The Lost World, and subsequent 1925 film adaptation. They have been used in a number of films and television programs since, including the 1933 film King Kong
King Kong
King Kong is a fictional character, a giant movie monster resembling a gorilla, that has appeared in several movies since 1933. These include the groundbreaking 1933 movie, the film remakes of 1976 and 2005, as well as various sequels of the first two films...

, and 1966's One Million Years B.C.
One Million Years B.C.
One Million Years B.C. is a 1966 British adventure/fantasy film starring Raquel Welch, set - loosely - in the time of cavemen. The film was made by Hammer Film Productions, and was a remake of the 1940 Hollywood film One Million B.C., and it recreates many of the scenes of that film...

. In the latter, animator Ray Harryhausen
Ray Harryhausen
Ray Harryhausen is an American film producer and special effects creator...

 had to add inaccurate bat-like wing fingers to his stop motion models in order to keep the membranes from falling apart, though this particular error was common in art even before the film was made. Pterosaurs were mainly absent from notable film appearances until 2001, with Jurassic Park III
Jurassic Park III
Jurassic Park III is a 2001 American science fiction film and the third of the Jurassic Park franchise. It is the only film in the series that is neither directed by Steven Spielberg nor based on a book by Michael Crichton, though numerous scenes in the movie were taken from Crichton's two books,...

. However, paleontologist Dave Hone has noted that even after the 40 intervening years, the pterosaurs in this film had not been significantly updated to reflect modern research. Among the errors he noted as persisting from the 1960s to the 2000s were teeth even in toothless species (the Jurassic Park III pterosaurs were intended to be Pteranodon, which translates as "toothless wing"), nesting behavior that was known to be inaccurate by 2001, and leathery wings, rather than the taut membranes of muscle fiber which was actually present and required for pterosaur flight.

A fictionalized mutation of a pterosaur was introduced in the 1956 Japanese film Rodan
Rodan (film)
Rodan, released in Japan as , is a 1956 Kaiju film produced by Toho Studios. It was the studio's first Kaiju movie filmed in color...

. The film was released by Toho
Toho
is a Japanese film, theater production, and distribution company. It is headquartered in Yūrakuchō, Chiyoda, Tokyo, and is one of the core companies of the Hankyu Hanshin Toho Group...

, the same studio responsible for Godzilla
Godzilla (1954 film)
is a 1954 Japanese science fiction film directed by Ishirō Honda and produced by Tomoyuki Tanaka. The film stars Akira Takarada, Momoko Kōchi, Akihiko Hirata and Takashi Shimura. The film tells the story of Godzilla, a giant monster mutated by nuclear radiation, who ravages Japan, bringing back the...

. The character later appeared in a number of Godzilla films between 1964 and 2004.

External links

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