Azhdarchidae

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Azhdarchidae
Plastic life reconstruction of Hatzegopteryx

Plastic life reconstruction of Hatzegopteryx

Temporal occurrence
Chalk ( Berriasian to Maastrichtian )
145 to 66 million years
Locations
Systematics
Archosauria
Ornithodira
Flugsaurier (Pterosauria)
Short-tailed pterosaur (Pterodactyloidea)
Azhdarchoidea
Azhdarchidae
Scientific name
Azhdarchidae
Nessov , 1984
Live representation of a large Azhdarchid with a wingspan of 10 meters compared to a human.
Skeleton diagram of a Hatzegopteryx in flight.

The azhdarchidae are a group of the extinct Flugsaurier (Pterosauria). The worldwide widespread group has been recorded since the early Cretaceous , but reached its greatest diversity in the late Cretaceous and only died out at the end of this epoch together with the dinosaurs . Azhdarchiden include the largest airworthy animals in the history of the earth. The largest representatives showed wingspans of approximately 10 to 11 meters and reached the height of today's giraffes with standing heights of over five meters. Azhdarchiden are among the easiest pterosaur groups to recognize for the layman - characteristic features include the long, edentulous jaws, the long neck, the proportionally short wings and the long hind legs. A large number of hypotheses have been postulated about the way of life of these animals; The latest study comes to the conclusion that Azhdarchids, like today's wading birds, preyed on various prey on the ground. Names factor in leading to the short-tailed pterodactyls counting (Pterodactyloidea) Azhdarchiden is the genus Azhdarcho whose name on Aždahā , the name of Dragon from the Persian back.

features

Azhdarchids are among the rarest vertebrate fossils, although they may have been common elements of the Cretaceous fauna. The very patchy fossil record of this group could be due to the preference for continental habitats, in which the fragile pterosaur skeletons show a lower conservation potential than in marine habitats, which were preferred by many better known pterosaur groups. Only Quetzalcoatlus sp. and Zhejiangopterus are each known by several fragmentary skeletons, while all other representatives are only based on highly incomplete remains. The known fossils suggest, however, that the skeletal structure of different representatives of the group differed only slightly; larger variations can only be found in the structure of the skull.

size

The body size of Azhdarchiden varies more than that of any other group of pterosaurs. The smallest known representative is Montanazhdarcho with a wingspan of about 2.5 meters. An analysis of the growth rings of the bones shows that the only known specimen was actually a fully grown animal and not a young animal. Complete skeletons are from the slightly larger Zhejiangopterus (3.5 meter wingspan) and the medium-sized Quetzalcoatlus sp. (5 meter wingspan) known. The largest representatives include Quetzalcoatlus nortrophi , Arambourgiania and Hatzegopteryx , which presumably reached wing spans of over 10 meters; This makes them by far the largest pterosaurs and the largest flight animals at all. These gigantic shapes are based only on very fragmentary fossils; so is Arambourgiania by an incomplete cervical vertebrae, Quetzalcoatlus nortrophi by a humerus and other fragments of the wing, and hatzegopteryx known by an upper arm bone, a femur and fragmentary skull bone. Early estimates of Quetzalcoatlus nortrophi's wingspan range from 11 to 21 meters; only with increasing understanding of the anatomy and body proportions of the group did estimates level off between 10 and 13 meters. A current study calculates a wingspan of 10.5 meters for Hatzegopteryx and Quetzalcoatlus nortrophi , but indicates that no reliable estimates are currently possible for Arambourgiania . An Azhdarchid with a wingspan of 10.5 meters would have reached a shoulder height of 2.5 meters on the ground and a total height of over 5 meters.

Estimates of the body weight of these animals are highly controversial. Numerous bones of the pterosaur skeleton were crisscrossed with air-filled chambers (pneumatized), which was originally interpreted as an adaptation to an extremely lightweight construction. For a long time, pterosaurs were therefore considered to be extremely light-weight sailors who were only able to flap their wings sporadically because of the reduced muscle mass to save weight. For a Quetzalcoatlus nortrophi with a wingspan of 10 meters, a 1974 study suggested a weight of only 50 to 60 kilograms. Meanwhile, many recent studies assume that the weight of pterosaurs is comparable to that of modern birds and bats of equal size; accordingly, an Azhdarchide with a wingspan of 10 meters can be estimated at up to 250 kg. Weight estimates of certain species depend primarily on the reconstructed wingspan; an animal with a wingspan of 13 meters would probably have been almost twice as heavy as an animal with a wingspan of 10 meters.

Paleontologists calculated a wingspan of 12 to 13 meters as the upper limit for a flightable Azhdarchid - with even larger wingspan, the load limit of the skeleton is exceeded and an effective take-off is no longer possible. Accordingly, Azhdarchids have brought their gigantism to the limits of what is physically feasible within their blueprint. Gigantism probably offered the animals a number of advantages, such as more efficient locomotion, greater protection against predators , the ability to survive long periods of low food supply, and more efficient heat regulation . As a result, the Azhdarchids, like many other gigantic groups of animals, may have grown so large simply because their skeletal blueprint and ecology allowed it.

skull

Reconstruction of the skull of Quetzalcoatlus sp.

The skull was lightly built, long and triangular in side view. In front of the eye sockets there was a very large skull window , the nasoantorbital window , which, among other things, housed the nostrils. While the eye sockets were limited to the lower part of the skull, the nasoantorbital window occupied almost the entire depth of the skull. In living animals, the jawbones had a horn beak , which was indicated by small openings in the jaw. The jaw muscles were only weakly developed; the most important sphincter muscle was the anterior wing muscle ( Musculus pterygoideus anterior ) as in today's birds . The occiput of the skull was aligned almost horizontally - the head joint was located on the underside of the skull, whereby the cervical spine was set at an angle of almost 90 ° relative to the longitudinal axis of the skull. Many pterosaurs showed eye-catching head crests that could extend from the jaws as well as from the top and back of the skull. In Azhdarchiden, a comb is only found in Quetzalcoatlus sp. detected, while the complete skull of Zhejiangopterus shows no evidence of a crest. The ridge of Quetzalcoatlus sp. is hump-shaped and was located above the posterior half of the nasoantorbital window.

The previously known skull remains can possibly be assigned to a “long-nosed” and a “short-nosed” blueprint. Zhejiangopterus , Quetzalcoatlus sp. and probably Alanqa had very long and low skulls that could be ten times longer than wide. The skull area in front of the nasoantorbital window, the rostrum, made up more than half the length of the jaw. In contrast, Bankonydraco and possibly the still undescribed “Javelina-Azhdarchide” and Azhdarcho had comparatively short skulls; the pine of Bankonydraco is only half as long in relation to its width as that of Quetzalcoatlus sp. Little is known about the skull of the largest representatives of the group. The jaws of Hatzegopteryx were almost half a meter wide - if the skull structure corresponded to that of the short-nosed Bankonydraco , the jaws would have been 2.5 meters and the entire skull approximately 3 meters long. If this estimate were correct, the skull of Hatzegopteryx would have been one of the longest of all known land animals.

Residual skeleton

Skeleton diagram of a Zhejiangopterus in quadruped locomotion on the ground.

Most of the skeleton adjoining the skull was riddled with air-filled chambers, including the entire wing. As in birds, these chambers were filled with air sacs that were in communication with the lungs.

The distinctive tubular cervical vertebrae are the most commonly found and best studied Azhdarchid fossils. By extending the third to the eighth cervical vertebrae, the neck was proportionally longer than that of all other pterosaurs: the fifth cervical vertebra was eight times as long as it was wide. The incomplete cervical vertebra of Arambourgiania suggests that the largest representatives showed a neck length of about three meters. Most of the cervical vertebrae lacked transverse processes , while the spinous processes were only pronounced as low ridges or were completely reduced. The articular processes were large and allowed only slight movements between the individual vertebrae, which made the neck relatively inflexible. The weak head joint suggests that the mobility of the head was also restricted.

The fuselage , although robustly built, was relatively small: even with the largest representatives it was probably only 70 centimeters long. The anterior vertebrae were fused together to form a notary , which possibly prevented the spine from bending when the wings flapped. Large muscle attachment points in the shoulder region lead Gregory Paul (2002) to suspect that the flight muscles of the largest representatives were as heavy as a full-grown person. Both shoulder and pelvic girdles were robust compared to other pterosaurs. The shoulder blade and raven bone were the same length, and the expansion of the pelvis behind the hip joint, the post-acetabular process, was large.

The humerus was built robustly, the bone shaft reached a width of eight centimeters in the largest representatives. As with all pterosaurs, the fourth metacarpal was very large, while the first three metacarpal bones were greatly reduced in size. In Azhdarchids, the fourth metacarpal bone was almost 2.5 times as long as the humerus - it was proportionally longer than in all other pterosaurs and the longest bone on the wing. The fourth metacarpal bone found its extension in the fourth finger, which was designed as a greatly enlarged flight finger. The flight finger was proportionally shorter than that of other pterosaurs and made up less than 50% of the total wing length. The four phalanges of the flying finger gradually became shorter outwards. The first three fingers were significantly smaller than the flight finger and were used for four-footed locomotion on the ground. The hind limbs were relatively longer than other pterosaurs, with the thigh bone reaching 80% of the length of the lower leg ( tibiotarsus ). The feet were small and narrow, but still more robust than many other pterosaurs.

Discovery story

This incomplete, sixty-two-centimeter cervical vertebra was the first fossil of an Azhdarchid to be given a name.
Jawbone of Alanqa .
Skeleton diagram of the Eurazhdarcho described in 2013 with the known skeleton parts. Most of the Azhdarchids are only very incomplete.

In 1959, Camille Arambourg described a tubular bone from Jordan as Titanopteryx ("gigantic wing") - this bone was the first fossil of an Azhdarchid to be given a name. The bone is incomplete, but still shows a length of 62 centimeters. Arambourg interpreted the bone as a metacarpal bone, which must have belonged to a giant pterosaur with a wingspan of about seven meters. It wasn't until the 1970s, after fossils of the Azhdarchid Quetzalcoatlus were discovered, that the bone was recognized as a cervical vertebra. Titanopteryx was later renamed Arambourgiania , as it turned out that the name Titanopteryx was already given to a fly at the time of description.

More complete fossils were finally recovered from Big Bend National Park ( Javelina Formation ) in Texas between 1972 and 1975 . The finds include a gigantic incomplete wing described in 1975 as Quetzalcoatlus northropi . In addition, several incomplete skeletons were recovered from smaller animals whose wingspan was about five meters; these specimens were attributed to a second, as yet unnamed Quetzalcoatlus species ( Quetzalcoatlus sp.). Although Quetzalcoatlus sp. It is about the best preserved Azhdarchia fossils to date, an exact scientific description is still pending. Today Quetzalcoatlus is one of the most popular pterosaurs.

In 1984 the Russian paleontologist Lev Nessov finally established the subfamily Azhdarchinae. The genus that gives it its name is the Azhdarcho ( Persian for "dragon") described at the same time , which is based on fragmentary bones from the early Upper Cretaceous of Uzbekistan . Only a few months after the publication of the name Azhdarchidae a work by Kevin Padian appeared , which provided the name Titanopterygiidae for the same group. Since Nessov's publication came before Padian's, the name Azhdarchinae has priority under the International Rules for Zoological Nomenclature . Two years later, Padian renamed the Azhdarchinae to Azhdarchidae and raised the group to the rank of family.

The most important discovery of the 1990s is Zhejiangopterus , known for several incomplete and badly crushed skeletons from the late Upper Cretaceous in China. Originally Zhejiangopterus was described in 1994 as a representative of the pterosaur group Nyctosauridae ; only in 1997 was Zhejiangopterus recognized as a representative of the Azhdarchidae. Currently the genus is considered to be the best studied of this group. Other genera described in the 1990s include Bennettazhia , which is based only on a humerus from the late Lower Cretaceous Oregon . The small Montanazhdarcho comes from the late Upper Cretaceous of Montana and was described in 1995 using a fragmentary skeleton. A fragment of a cervical vertebra, already described in 1914 and known today as Bogolubovia , was also placed among the Azhdarchidae in 1991. However, the fossil is now considered lost and the validity of the genus has been questioned.

In 2002 another gigantic representative of the family was described with Hatzegopteryx . A very fragmentary example comes from the late Upper Cretaceous in the Romanian Hațeg Basin and includes fragments of the skull and a fragmentary humerus. Phosphatodraco , described in 2003, is known for a fragmentary cervical spine from phosphate-rich deposits of the Ouled-Abdoun-Basin in Morocco. Somewhat more complete remains from the Middle Upper Cretaceous of Hungary, which include a complete jaw among other things, were baptized Bakonydraco in 2005 . Other, but very fragmentary, representatives were described in 2007 with Aralazhdarcho from Uzbekistan and in 2008 with Volgadraco from Russia. A second Azhdarchid from Morocco, Alanqa , was described in 2010 and is based on fragmentary pine trees. In 2011 the description of Navajodactylus from the late Upper Cretaceous New Mexico was published. The genus is of controversial validity as it is based only on the top of the first phalanx of the flying finger. In 2013, Eurazhdarcho, a second genus of Azhdarchids from the late Upper Cretaceous of Romania, was published.

Systematics

The exact relationships with other pterosaur groups are controversial. For classification of pterosaurs are two competing approaches that are based on different data sets, some bring their own descriptions and definitions of parent groups and differ in important ways. Modern systematic analyzes are mostly derived from one of these two approaches. The first approach was introduced by Alexander Kellner (2003) and sees the Azhdarchidae as a sister group of the Tapejaridae ( Tapejara + Tupuxuara ); both families are summarized as Azhdarchoidea. The Azhdarchoidea are subordinated to the Dsungaripteroidea by Kellner , one of two groups within the short-tailed pterosaurs (Pterodactyloidea). The second approach by David Unwin (2003) concludes that Tupuxuara was more closely related to the Azhdarchids than to Tapejara . With Tupuxuara as a sister group, the Azhdarchids form the group Neoazhdarchia , which together with Tapejara or the Tapejaridae forms the group Azhdarchoidea. According to Unwin, the Azhdarchoidea belong to a group called Lophocratia within the short-tailed pterosaurs . Only since 2008 have the Chaoyangopteridae been differentiated as an independent group, which may also have been closely related to the Azhdarchids. The relationships within the Azhdarchidae cannot be broken at the moment.

Two cladograms follow : the left illustrates the kinship hypothesis of Kellner (2003); the right one from Unwin (2003).

  Azhdarchoidea  

 Azhdarchidae


  Tapejaridae  

 Tapejara


   

 Tupuxuara




Template: Klade / Maintenance / Style
  Azhdarchoidea  

 Tapejaridae


  Neoazhdarchia  

 Azhdarchidae


   

 Tupuxuara




Template: Klade / Maintenance / Style

Tribal history and distribution

Upper Cretaceous paleogeographic map showing fossil deposits that contained more than one Azhdarchid species.

Little is known about the origin of the Azhdarchids. Until recently, greatly elongated cervical vertebrae from the Upper Jurassic of Tanzania and the Jurassic-Cretaceous border of England were considered to be the oldest evidence of Azhdarchids. Brian Andres and Ji Qiang (2008) showed, however, that these cervical vertebrae are likely to be assigned to another pterosaur group, the Ctenochasmatidae . In both groups, which are only distantly related to one another, greatly elongated cervical vertebrae developed independently of one another , which could show that both groups occupy similar ecological niches . A much more recent find is currently considered to be possibly the oldest Azhdarchid fossil - a fragmentary cervical vertebra from the Berriasian (Lower Cretaceous, 145 to 140 Mya ) of Romania described in 2010 . Should this evidence be confirmed, the group would have been proven over a period of about 80 million years and would have existed longer than any other pterosaur group.

Azhdarchiden apparently reached their heyday during the Upper Cretaceous - all named representatives come from this epoch. Fossils were mainly discovered in North America, Europe, Asia, and North Africa; isolated finds are known from Argentina, Japan and Australia. This means that Azhdarchids have been found on all continents with the exception of Antarctica. Various rock formations contain fossils of more than one Azhdarchid species: The giant form Quetzalcoatlus northropi and two medium-sized species ( Quetzalcoatlus sp. And an as yet unnamed representative) have been found in the Javelina Formation in Texas . In the Two Medicine Formation of Montana , in addition to the small form Montanazhdarcho, there is an indefinite, significantly larger representative. In the dinosaur park formation of Alberta there is probably a giant form and a medium-sized representative, while in the Romanian Hațeg basin the very large Hatzegopteryx occurs together with the small representative Eurazhdarcho . The species that occur together in each case could have occupied different ecological niches in order to avoid competition.

Azhdarchids became extinct with the Cretaceous Tertiary mass extinction 66 million years ago. An important reason for the extinction is probably the size of these animals: large animals are generally highly specialized, have low population densities and reproduce slowly, which is why they are less able to adapt to changing environmental conditions than small and unspecialized animals. Most other pterosaur groups disappear from the fossil record about 30 million years before mass extinction. However, it remains controversial whether pterosaurs were actually greatly decimated in their diversity long before mass extinction, or whether fossils simply remain unknown because there are no corresponding fossil deposits (the so-called deposit effect). In this context the finds of pterosaurs including representatives of the Azhdarchidae, the Nyctosauridae and the Pteranodontidae from the Ouled-Abdoun-Basin are of importance.

Paleobiology

flight

Skeleton reconstruction of a Quetzalcoatlus in flight, exhibited in the Senckenberg Museum in Frankfurt am Main .
Flight silhouettes of A: Quetzalcoatlus , B: Wandering Albatross and C: Andean condor in comparison. Not to scale.
Comparison of the length-width ratio ( aspect ratio ) and the surface load ( wing loading ) of the wings of birds and pterodactyls (Azhdarchiden and Pteranodon ). Azhdarchiden fall into the field of overland sailors ( thermal soarers ).

The question of how pterosaurs and especially large representatives such as Azhdarchiden started their flight is controversial. Traditionally, a start is assumed with the help of the hind legs, as can be seen in today's birds. Chatterjee and Templin (2004) argued that Quetzalcoatlus nortrophi was only able to take off because of its very low body mass of 70 kilograms; a start can take place when the animal stands up on two legs and runs against the wind or pushes itself off a slope. More recent studies suggest, however, that pterosaurs started from a quadruped posture with the help of their forelimbs, similar to today's bats. In this way, the large flight muscles can be used to lift the body; the forelimbs of large Azhdarchiden are strong enough to lift a weight of approximately 500 kg into the air.

Donald Henderson (2010) hypothesized that large Azhdarchids like Quetzalcoatlus nortrophi could have been flightless secondarily. The wings are too short for effective flight, and the hind limbs are better adapted to locomotion on the ground than other pterosaurs. Henderson calculated the weight of Quetzalcoatlus nortrophi at 544 kilograms, meaning that this animal was simply too heavy to fly. Mark Witton and Michael Habib (2010), on the other hand, argue that Henderson assumed a torso that was too large for the weight estimation and thus a weight of 200 to 250 kg is more realistic. Even large Azhdarchids would show all the adaptations to a flight that are also found in smaller pterosaurs.

Witton and Darren Naish (2008) argue that the short and wide wings are adapted for flying over land. With the due to the wide wing low wing loading Azhdarchiden might have had thermals used. Short and wide wings would have made the animals more manoeuvrable and also enabled quick take-off and ascent, which would have been advantageous in areas rich in vegetation, for example. Similar length ratios of the wings are found in modern land-dwelling birds such as the Andean condor , while marine sailors such as the wandering albatross generally tend to have long and slender wings.

Traditionally, large pterosaurs are considered to be extremely lightweight, which would have allowed them to glide much slower than today's birds. If a weight is assumed that is comparable to that of today's birds and bats, this picture changes drastically: Witton and Habib (2010) calculate that a 200 kilogram Azhdarchide with a wingspan of 10 meters becomes powerful for about two minutes after takeoff Was able to maintain wing beats at which the animal reached speeds of over 100 km / h before the animal went into a slightly slower soaring flight. Such an Azhdarchide was able to cover more than 16,000 kilometers without stopping, more than any other animal.

Locomotion on the ground

Fossil footprints of an Azhdarchid. A: A seven meter long track, B: hand print, C: rear foot print.

Fossil footprints of walking and running pterosaurs show that many species were significantly more competent at locomotion on the ground than traditionally assumed. Haenamichnus , discovered in Korea, is attributed to a very large representative of the Azhdarchidae: the hind footprints measure 35 centimeters in length, which indicates an animal with a shoulder height of almost three meters and a wingspan of over 10 meters. These footprints are currently the only ones that can be ascribed to a particular pterosaur group; no other known group could have left footprints of this size. One of the tracks is seven meters long, making it the longest known track of a pterosaur. This track sequence shows that the long limbs of the Azhdarchids enable fast and efficient locomotion on the ground: the track sequence is narrow, which shows limbs standing vertically under the body, and the hind footprints regularly overlay the handprints previously left. The toes were provided with fleshy pads, with no claw prints.

ecology

A group of Azhdarchids strides through a fern prairie looking for prey.

In 1975 Douglas Lawson put forward the first hypothesis about the diet of an Azhdarchid in a report on the newly discovered pterosaur Quetzalcoatlus . Although pterosaurs were widely viewed as fish-eaters at the time, Lawon argued that Quetzalcoatlus may have been a scavenger that used its long neck to penetrate carcasses. The fossils of this genus would appear in continental deposits far from the coast and would have been found together with the bones of the herbivorous sauropod dinosaurs. Various later authors criticized this idea; the connection to the sauropod fossils was accidental and the neck too stiff to be able to penetrate the carcass.

Numerous other hypotheses have been put forward since Lawson's Scavenger Hypothesis. When Langston (1981) speculated that Quetzalcoatlus might have groped for invertebrates with its beak in the mud; structures of arthropods found together with the bones of the pterosaur would indicate this . Against this hypothesis, it was argued that the connection with the trace fossils was accidental, the neck too stiff and the shape of the beak unsuitable; In addition, there was no evidence of pressure-sensitive Herbst bodies or similar structures in the jawbones, which are used in many modern birds to recognize prey in the silt. Various other authors suggested that the Azhdarchids waded through shallow waters to hunt down prey. The long legs as well as the long neck and skull support this thesis; the proportionally small feet, however, were probably not suitable for wading on soft sediment. Still other authors suggested that some members of the group might have eaten fruit or hunted less well-flying animals in the air.

Most of the studies hypothesized that Azhdarchids might have been fish-eaters. Lev Nessov (1984) suspected that Azhdarcho and other Azhdarchids flew through the water with their beaks while in flight or while swimming, in order to snap at contact with prey. This type of diet is found in today's scissors beaks and enables these birds to catch prey even in murky waters. Critics note that scissor beaks show numerous adaptations to this very specialized diet, such as a reinforced temporomandibular joint and very robust cervical vertebrae, which are not found in Azhdarchids. Meanwhile, various authors suggested that Azhdarchiden stabbed their beaks into the water in flight to prey on fish, similar to today's gulls , terns and frigate birds . The long neck and skull would have enabled these pterosaurs to prey on fish without their wings touching the surface of the water. Opponents of the hypothesis argue that the cervical spine was almost at right angles to the long axis of the skull; thus the animals would not have been able to lay their heads and necks in one line when they hit. In addition, the neck was too rigid and the tip of the snout was not bent downwards, as is the case with many modern birds that show this way of feeding.

The most recent hypothesis was postulated by Witton and Naish (2008). According to these researchers, Azhdarchiden paced dry terrain to opportunistically ingest small to medium-sized vertebrates and large invertebrates, as well as sporadically carrion, eggs or fruit. A similar diet can be found in some of today's walking birds , for example in the real storks . As the researchers argue, the majority of the Azhdarchid fossils were discovered in river sediments that were deposited inland. Representatives of the group seem to have frequented continental habitats, such as forest and bush landscapes and river plains. The proportionally small feet, equipped with fleshy pads and only small claws, would have been most efficient on firm ground. The long legs were ideal for walking through vegetation, the downward-pointing beak made it easy to reach the ground, and the long, stiff neck could have been used, among other things, to peek for prey from an elevated position or to look around the head Approach prey before they are startled by the pterosaur's kicks. Witton (2013) contemplates that some Azhdarchids may have gone foraging in groups, as fossils of several individuals are occasionally found together. The largest Azhdarchids occur in the late Upper Cretaceous when medium-sized carnivorous dinosaurs were strikingly rare. Witton (2013) therefore speculates that Azhdarchids may have at least partially occupied the ecological niche of medium-sized carnivores in the late Upper Cretaceous.

literature

Individual evidence

  1. ↑ a b Witton (2013): Pterosaurs. Natural history, evolution, anatomy. P. 249.
  2. ^ Witton (2013): Pterosaurs. Natural history, evolution, anatomy. P. 244.
  3. ^ Witton and Naish (2008): A reappraisal of Azhdarchid Pterosaur Functional Morphology and Paleoecology . P. 1.
  4. ↑ a b c Attila Ősi, Éric Buffetaut , Edina Prondvai: New pterosaurian remains from the Late Cretaceous (Santonian) of Hungary (Iharkút, Csehbánya Formation). In: Cretaceous Research. Vol. 32, No. 4, 2011, ISSN  0195-6671 , pp. 456-463, doi: 10.1016 / j.cretres.2011.01.011 .
  5. ^ Witton (2013): Pterosaurs. Natural history, evolution, anatomy. Pp. 248-249.
  6. ^ A b c Brian Andres, Ji Qiang: A new pterosaur from the Liaoning Province of China, the phylogeny of the Pterodactyloidea, and convergence in their cervical vertebrae. In: Palaeontology. Vol. 51, No. 2, 2008, ISSN  0031-0239 , pp. 453-469, here pp. 453 and 462-463, doi: 10.1111 / j.1475-4983.2008.00761.x .
  7. ↑ a b c d Witton (2013): Pterosaurs. Natural history, evolution, anatomy. P. 251.
  8. ↑ a b Witton (2013): Pterosaurs. Natural history, evolution, anatomy. Pp. 249-251.
  9. ↑ a b c d e f Witton (2013): Pterosaurs. Natural history, evolution, anatomy. Pp. 244-248.
  10. ↑ a b c d e f g h Mark P. Witton, Michael B. Habib: On the Size and Flight Diversity of Giant Pterosaurs, the Use of Birds as Pterosaur Analogues and Comments on Pterosaur Flightlessness. In: PLoS ONE . Vol. 5, No. 11, 2010, e13982, doi: 10.1371 / journal.pone.0013982 .
  11. ↑ Mark P. Witton: A new approach to determining pterosaur body mass and its implications for pterosaur flight. In: Zitteliana. Series B: Treatises of the Bavarian State Collection for Paleontology and Geology. Vol. 28, 2008, ISSN  1612-4138 , pp. 143–158, digital version (PDF; 6.88 MB) .
  12. ↑ a b Witton (2013): Pterosaurs. Natural history, evolution, anatomy. P. 58.
  13. ^ A b c Witton and Naish (2008): A reappraisal of Azhdarchid Pterosaur Functional Morphology and Paleoecology . Pp. 3-5.
  14. ↑ a b c Mark Witton: Titans of the skies: azhdarchid pterosaurs. In: Geology Today. Vol. 23, No. 1, 2007, ISSN  0266-6979 , S 33-38, doi: 10.1111 / j.1365-2451.2007.00596.x .
  15. ^ Witton (2013): Pterosaurs. Natural history, evolution, anatomy. Pp. 252-253.
  16. ↑ a b c d e Witton (2013): Pterosaurs. Natural history, evolution, anatomy. P. 254.
  17. ^ Witton (2013): Pterosaurs. Natural history, evolution, anatomy. P. 37 and 58.
  18. ^ A b Witton and Naish (2008): A reappraisal of Azhdarchid Pterosaur Functional Morphology and Paleoecology . P. 5.
  19. ^ Peter Wellnhofer, Eric Buffetaut, Paul Gigase: A pterosaurian notarium from the Lower Cretaceous of Brazil. In: Paleontological Journal . Vol. 57, No. 1/2, 1983, pp. 147-157, doi: 10.1007 / BF03031757 .
  20. ^ Gregory S. Paul : Dinosaurs of the Air. The Evolution and Loss of Flight in Dinosaurs and Birds. Johns Hopkins University Press, Baltimore MD et al. 2002, ISBN 0-8018-6763-0 , p. 333.
  21. ↑ a b Witton (2013): Pterosaurs. Natural history, evolution, anatomy. P. 255.
  22. ↑ Alexander O. Averianov: The osteology of Azhdarcho lancicollis Nessov, 1984 (Pterosauria, Azhdarchidae) from the late Cretaceous of Uzbekistan. In: Proceedings of the Zoological Institute of the Russian Academy of Sciences. Vol. 314, No. 3, 2010, ISSN  0206-0477 , pp. 264-317, here p. 265, digital version (PDF; 4.63 MB) .
  23. ↑ Brian Andres, Timothy S. Myers: Lone Star Pterosaurs. In: Transactions of the Royal Society of Edinburgh. Earth and Environmental Science. Vol. 103, No. 3/4, 2012, ISSN  1755-6910 , pp. 383-398. here p. 391, doi: 10.1017 / S1755691013000303 .
  24. ↑ a b Xabier Pereda Suberbiola Nathalie Bardet, Stéphane Jouve S, Mohamed Iarochène, Baâdi Bouya, Mbarek Amaghzaz: A new azhdarchid pterosaur from the Late Cretaceous phosphates of Morocco. In: Geological Society, London, Special Publications. Vol. 217, No. 3, 2003, pp. 79-90.
  25. ^ A b Nicholas R. Longrich, David M. Martill, Brian Andres: Late Maastrichtian pterosaurs from North Africa and mass extinction of Pterosauria at the Cretaceous-Paleogene boundary. In: PLoS Biology. Vol. 16, No. 3, 2018, p. E2001663, doi: 10.1371 / journal.pbio.2001663 .
  26. ↑ a b c Mátyás Vremir, Alexander WA Kellner, Darren Naish, Gareth J. Dyke : A New Azhdarchid Pterosaur from the Late Cretaceous of the Transylvanian Basin, Romania: Implications for Azhdarchid Diversity and Distribution. In: PLoS ONE. Vol. 8, No. 1, 2013, p. E54268, doi: 10.1371 / journal.pone.0054268 .
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  37. ^ Witton and Naish (2008): A reappraisal of Azhdarchid Pterosaur Functional Morphology and Paleoecology . P. 8.
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  42. ^ Douglas A. Lawson: Pterosaur from the Latest Cretaceous of West Texas: Discovery of the Largest Flying Creature. In: Science . Vol. 187, No. 4180, 1975, pp. 947-948, doi: 10.1126 / science.187.4180.947 , PMID 17745279 .
  43. ↑ Attila Ősi, David B. Weishampel , Coralia M. Jianu: First evidence of azhdarchid pterosaurs from the Late Cretaceous of Hungary. In: Acta Palaeontologica Polonica. Vol. 50, No. 4, 2005, ISSN  0567-7920 , pp. 777-787, online .
  44. ^ Witton and Naish (2008): A reappraisal of Azhdarchid Pterosaur Functional Morphology and Paleoecology . Pp. 12-14.
  45. ↑ a b Witton (2013): Pterosaurs. Natural history, evolution, anatomy. P. 258.