Azhdarchidae

Plastic reconstruction of live Hatzegopteryx

• World (except Antarctica )

The Azhdarchidae are a group of extinct pterosaurs ( Pterosauria ). The globally widespread group is detected since the early Cretaceous period, but achieved their greatest diversity in the Late Cretaceous and died at the end of this period along with the dinosaurs out. Azhdarchiden include the largest flying animals of the earth's history with a. The largest representatives showed wingspans estimated at 10 to 11 meters and reached level heights of over five meters, the height of today's giraffes. Azhdarchiden are among the most easily recognizable to the layman flight Aryan groups - characteristic features include the long edentulous jaw, the long neck, the proportionally short wings and long hind legs with a. For the life of these animals, a variety of hypotheses has been postulated; the most recent study concludes that Azhdarchiden nachstellten as today's Ciconiiformes at the bottom of various prey animals. The name derives for the short-tailed pterosaurs ( Pterodactyloidea ) scoring Azhdarchiden is the genus Azhdarcho whose name dates back to the name for dragon from Persian.

• 5.1 flight
• 5.2 locomotion on the ground
• 5.3 Ecology

Features

Azhdarchiden are among the rarest vertebrate fossils, although it is perhaps these were common elements of the Cretaceous faunas. 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 value than in marine habitats that were preferred by many better-known pterosaur groups. Only Quetzalcoatlus sp. and Zhejiangopterus are known by each of several fragmentary skeletons, while all the other representatives are based only on highly incomplete residues. The known fossils suggest, however, that the skeleton differed only slightly with various representatives of the group; larger variations are found only in the structure of the skull.

Size

The height varies more than any other pterosaur group at Azhdarchiden. The smallest known representative is Montanazhdarcho with a wingspan of about 2.5 meters. An analysis of the growth rings of the bone shows that it was indeed a full-grown animal the only known copy, and not a young animal. Complete skeletons of the only slightly larger Zhejiangopterus ( 3.5 meters wingspan ) and the medium-sized Quetzalcoatlus sp. (5 meter wingspan ) are known. One of the greatest representatives include Quetzalcoatlus nortrophi, Arambourgiania and Hatzegopteryx, which probably reached wingspans of over 10 meters; so it is by far the largest pterosaurs, and the largest flying animals ever. These gigantic forms based only on very fragmentary fossils; so Arambourgiania is known by an incomplete cervical vertebrae, Quetzalcoatlus nortrophi by an upper arm bone and other fragments of the wing, and Hatzegopteryx by a humerus, a femur and fragmentary cranial bones. Early estimates of the wingspan of Quetzalcoatlus nortrophi range 11 to 21 meters; only with increasing understanding of anatomy and body proportions of the group estimates commuted a 10 to 13 meters. A recent study calculated 10.5 meter wingspan Quetzalcoatlus for Hatzegopteryx and nortrophi, but points out that there are currently no reliable estimates for Arambourgiania possible. A Azhdarchide with a wingspan of 10.5 meters would have reached a shoulder height of 2.5 meters and a total height of over 5 meters on the ground.

Estimates of body weight of these animals are highly controversial. Numerous bones of the pterosaur skeleton were permeated with air-filled chambers ( pneumatized ), which was originally interpreted as an adaptation to an extreme lightweight construction. Long pterosaurs were thus held to be extremely lightweight sailors who were too sporadic wing beats in a position because of reduced muscle mass to reduce weight only. For a Quetzalcoatlus nortrophi with a wingspan of 10 meters, a weight was suggested by only 50 to 60 kg of a 1974 study. Many recent studies, meanwhile, go on the assumption that the weight of pterodactyls is comparable to the same large modern birds and bats; therefore, a Azhdarchide with a wingspan of 10 meters up to 250 kg can be estimated. Weight estimates of certain species depend mainly on the reconstructed wing span; as 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 12-13 meters as the upper limit for an airworthy Azhdarchiden - with even larger spans, the load limit of the skeleton is exceeded and an effective start no longer possible. Thus Azhdarchiden have expressed their gigantism to the limits of what is physically possible within their blueprint. The gigantism offered the animals probably a number of advantages, such as more efficient locomotion, a greater protection against predators, the persistence prolonged periods of low food availability and a more efficient heat regulation. Thus were Azhdarchiden, as well as many other animal groups with gigantism, possibly simply because of the size, because their skeleton plan and their ecology would allow.

The skull was lightly built, long and triangular in side view. In front of the eye sockets, there was a very large skull window that Nasoantorbitalfenster which housed the nostrils among others. While the eye sockets were limited to the lower part of the skull, the Nasoantorbitalfenster club collected almost the entire depth of the skull. The jawbone wore in the living animal a beak made ​​of horn, whereupon small openings in the jaw have. The jaw muscles were only weak; the most important sphincter was like modern birds, the front wing muscle (musculus pterygoid anterior). The occiput of the skull was aligned approximately horizontally - that is, the joint head was located on the underside of the skull, whereby the cervical ansetzte at an angle of almost 90 ° relative to the longitudinal axis of the head. Many pterosaur head crests showed clearly that could come from both the jaws and from the top and back of the skull. In Azhdarchiden a comb is so far only in Quetzalcoatlus sp. demonstrated during the complete skull of Zhejiangopterus shows no indication of a comb. The crest of Quetzalcoatlus sp. is hump -shaped and was located on the rear half of Nasoantorbitalfensters.

The previously known skull fragments may be able to a " long-snouted " and a " kurzschnäuzigen " are assigned to the plan. Zhejiangopterus, Quetzalcoatlus sp. and probably Alanqa showed very long and low skull, which could be longer than wide ten times. The skull area before Nasoantorbitalfenster, the Rostrum, accounted for more than half of jaw length. In contrast, exhibited Bankonydraco and possibly undescribed " Javelina - Azhdarchide " and Azhdarcho relatively short skull; the jaw of Bankonydraco is in proportion to its width only half as long as that of Quetzalcoatlus sp. Little is known about the skull of the greatest representatives of the group. The jaws of Hatzegopteryx reasonably almost half a meter in width - equivalent to the cranial structure of the kurzschnäuzigen Bankonydraco, the jaw would have been 2.5 meters and the whole skull approximately 3 meters long. If that were to this estimate, the skull of Hatzegopteryx would have counted among the longest of all known of terrestrial animals.

Rest of the skeleton

The majority of the skull to subsequent skeleton was laced with air-filled chambers, including the entire wing. These chambers are filled with air as in birds bags which were in contact with the lungs.

The characteristic tubular neck vertebrae are the most commonly found and best studied Azhdarchiden fossils. By lengthening the third to eighth cervical vertebra of the neck was proportionally longer than in all other pterosaurs: the fifth cervical vertebra was about eight times as long as wide. The incomplete cervical vertebrae of Arambourgiania suggests that the greatest representatives showed a neck length of about three meters. In most cervical vertebrae lacking transverse processes, while the spinous processes were reduced or fully pronounced only as low ridges. The articular processes were large and allowed only small movements between the individual vertebrae, the neck of which made ​​relatively inflexible. The weak head joint suggests that the mobility of the head was limited.

The hull, though ruggedly built, was relatively small: even the largest representatives presumably he measured only 70 centimeters in length. The anterior dorsal vertebrae were fused together to form a Notarium, possibly preventing bending of the spine while flapping its wings. Large muscle attachment sites in the shoulder region can Gregory Paul ( 2002) suggest that the flight muscles of the greatest representatives were as heavy as an adult human. Both shoulder and pelvic girdle were robust in comparison with other pterodactyls. Scapula and coracoid met each other in length and located behind the hip joint extension of the pelvis, Postacetabularprozess was great.

The humerus was built to last, the bone shaft reached at the largest representatives of a width of eight centimeters. As with all pterodactyls of the fourth metacarpal bone was very large, while the first three metacarpals were greatly reduced in size. In Azhdarchiden the fourth metacarpal bone was almost 2.5 times as long as the upper arm bone - so it was longer in proportion than in any other pterodactyls and the longest bone of the wing. The fourth metacarpal bone found its extension in the fourth finger, which was designed as a greatly enlarged flight finger. The flight was proportional finger shorter than in other pterosaurs, and made less than 50 % of the total wing length from. The four phalanges of the finger were successively shorter flight to the outside. The first three fingers were significantly smaller than the flight of his fingers and served the quadrupedal locomotion on the ground. The hind limbs were in proportion longer than in other pterosaurs, with the femur reached 80 % of the length of the lower leg ( tibiotarsus ). The feet were small and narrow but still robust than many other pterodactyls.

Discovery history

1959 described Camille Arambourg a tubular bone from Jordan as Titanopteryx ( " giant wings" ) - this bone was thus the first fossil of a Azhdarchiden, which received a name. The bone is incomplete, but still shows a length of 62 centimeters. Arambourg interpreted the bone as metacarpal bones, which must have belonged to a giant pterosaur with a wingspan of about seven meters. It was only in the 1970s after fossils of Quetzalcoatlus Azhdarchiden were discovered, the bone has been recognized as cervical vertebrae. Later Titanopteryx was renamed Arambourgiania, as it turned out, that the name was already taken Titanopteryx at the time of the description to a fly.

More complete fossils were eventually salvaged 1972-1975 from the Big Bend National Park ( Javelina Formation) in Texas. The finds include a gigantic incomplete wing, which was founded in 1975 described 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 - type ( Quetzalcoatlus sp.). Despite the fact that Quetzalcoatlus sp. is the best preserved until today Azhdarchien fossils, an accurate scientific description is pending. Today Quetzalcoatlus is one of the most famous in the public pterodactyls.

In 1984, the Russian paleontologist Lev Nessov finally to the subfamily Azhdarchinae. Name -giving genus is the Azhdarcho same time as described (Persian for "Dragon "), which is based on fragmentary bone from the Early Cretaceous of Uzbekistan. Only a few months after the publication of the name Azhdarchidae appeared a work by Kevin Padian, which provided the name Titanopterygiidae for the same group. Since Nessovs publication before that appeared from Padian, has the name Azhdarchinae in the International Regulations for Zoological Nomenclature priority. Two years later, Padian named to the Azhdarchinae in Azhdarchidae and thus raised the group to the rank of a family.

The most important discovery of the 1990s is Zhejiangopterus, which is known by several incomplete and heavily crushed skeletons from the Late Cretaceous of China. Originally Zhejiangopterus was described in 1994 as representative of the pterosaur group Nyctosauridae; until 1997 Zhejiangopterus was recognized as a representative of Azhdarchidae. Currently, the genus is considered to be the best studied of this group. Other species described in the 1990s close Bennettazhia with a merely based on a humerus from the Late Cretaceous of Oregon. From the Late Cretaceous of Montana the diminutive Montanazhdarcho, which was described in 1995 based on a fragmentary skeleton comes. A 1914 described fragment of a cervical vertebra, which is known as Bogolubovia today, was in 1991 also provided to the Azhdarchidae. The fossil is now, however, to be lost and the validity of the genus is disputed.

2002 has been described with Hatzegopteryx another gigantic representative of the family. A very fragmentary specimen from the late Cretaceous of Romania Haţeg Basin and includes skull fragments and a fragmentary humerus with a. Phosphatodraco described in 2003, is known from a fragmentary cervical spine from phosphate- rich deposits of Morocco. Something more complete remains from the middle Cretaceous of Hungary, including, among other things, a complete jaw with, were baptized in 2005 Bakonydraco. More, but only very fragmentary surviving representatives were described with Aralazhdarcho from Uzbekistan and 2008 Volgadraco from Russia in 2007. A second Azhdarchide from Morocco, Alanqa, was described in 2010 and is based on fragmentary jaws. 2011, the description of Navajodactylus from the Late Cretaceous of New Mexico has been released. The genus is of questionable validity, since it is based only on the upper end of the first phalanx of the finger flight. 2013 was published with Eurazhdarcho a second Azhdarchiden genus from the Late Cretaceous of Romania.

System

The exact relationships with other pterosaur groups are controversial. For the classification of pterosaurs are two competing approaches which are based on different data sets, some bring their own descriptions and definitions of parent groups and differ from each other in important ways. Modern systematic analyzes are usually derived from either 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 be assumed by the waiter Dsungaripteroidea, one of two groups within the short-tailed pterosaurs ( Pterodactyloidea ). The second approach of David Unwin (2003) concludes that Tupuxuara was more closely related to the Azhdarchiden than Tapejara. With Tupuxuara as a sister group to the Azhdarchiden accordingly form the group Neoazhdarchia forming the group Azhdarchoidea together with Tapejara or Tapejaridae. According to Unwin, the Azhdarchoidea belong to within the short-tailed pterosaurs a Lophocratia mentioned group. Only since 2008, the Chaoyangopteridae be distinguished as a separate group, which could have been possibly also closely related to the Azhdarchiden. The relationships within the Azhdarchidae can not currently be resolved.

Here are two cladograms: the left illustrates the relationship hypothesis of Kellner ( 2003); the right those of Unwin ( 2003).

Azhdarchidae

Tapejara

Tupuxuara

Tapejaridae

Azhdarchidae

Tupuxuara

Phylogeny and distribution

Little is known about the origin of Azhdarchiden. Until recently, strongly elongated cervical vertebrae from the Upper Jurassic of Tanzania and the Jurassic - Cretaceous boundary of England as the oldest evidence of Azhdarchiden were. Brian Andres and Ji Qiang (2008) showed, however, that these vertebrae are probably attributable to another pterosaur group, the Ctenochasmatidae. In both, only distantly related to each other groups strongly elongated cervical vertebrae have formed independently of each other, which could show that both groups in similar ecological niches. Currently, a significantly younger Fund is considered to be possibly the oldest Azhdarchiden Fossil - a 2010 described fragmentary cervical vertebrae from the Berriasian ( Lower Cretaceous, 145-140 Mya ) of Romania. If confirmed, this evidence, the group for a period of about 80 million years would be detected and would thus longer exists than any other pterosaur group.

Azhdarchiden apparently reached their heyday during the Upper Cretaceous - all designated representative date from this era. Fossils have been found mainly in North America, Europe, Asia and North Africa; isolated finds are known from Argentina, Japan and Australia. This Azhdarchiden are detected on all continents with the exception of Antarctica. Various rock formations contain fossils of more than one Azhdarchiden species: thus, in the Javelina Formation in Texas, the giant form Quetzalcoatlus Northropi and two medium-sized species detected ( sp Quetzalcoatlus and a yet unnamed representative. ). In the Two Medicine Formation of Montana occurs in addition to the small form Montanazhdarcho on an indefinite, much larger representative. In the Dinosaur Park Formation of Alberta probably a giant form, as well as a medium-sized representative is present, while in the Romanian Haţeg Basin occurs the very large Hatzegopteryx together with the small representative Eurazhdarcho. The species occurring in each case together could have occupied different ecological niches to avoid competition.

Azhdarchiden died with the Cretaceous-Tertiary mass extinction of 66 million years ago. An important reason for the extinction is probably in body size of these animals: Large animals are generally highly specialized, have low population densities and propagate only slowly so that they can adapt to changing environmental conditions less rapidly than small and unspecialized animals. Most other pterosaur groups disappear already about 30 million years before the mass extinction from the fossil record, and in the latest Cretaceous only witnessed a single upper arm bone, the presence of a second group of Nyctosauridae. Remains controversial, however, whether pterosaurs were actually decimated long before the mass extinction in its diversity, or whether fossils therefore remain unknown simply because corresponding fossil sites are missing ( the so-called deposits effect).

Paleobiology

Flight

The question of how pterosaurs and especially great representative as Azhdarchiden is controversially discussed their flight took off. Traditionally, a start was adopted with the help of the hind legs, as is seen in modern birds. Chatterjee and Templin (2004) argued that Quetzalcoatlus nortrophi is only capable by its very low body mass of 70 kg at the start; A start could be made when the animal rearing on two legs and running against the wind, or pushes off from a slope. Recent studies suggest, however, that pterosaurs took off from a quadrupedal stance, with the help of the front limbs, similar to today's bats. In this way the large flight muscles can be used to Emporhieven of the body; the forelimbs great Azhdarchiden be strong enough to carry a weight of approximately 500 kg in the air.

Donald Henderson ( 2010) hypothesized that large Azhdarchiden like Quetzalcoatlus nortrophi might have been secondarily flightless. So the wings are too short for an actual flight, and the hind limbs better adapted to locomotion on the ground than in other pterosaurs. The weight of Quetzalcoatlus nortrophi calculated Henderson to 544 kg, so is this animal was simply too heavy to fly. Mark Witton and Michael Habib (2010) argue that Henderson for weight estimation assumed a large trunk and thus a weight of 200 to 250 kg is more realistic. Even large Azhdarchiden would all adjustments to a flight show that are also found in smaller pterodactyls.

Witton and Darren Naish (2008) argue that the short and broad wings are adapted to a fly over land. With the low wing loading caused by the broad wings Azhdarchiden might have used thermal updrafts. Short and broad wings were the animals made more agile and also allowed for a quick start to rise, which would have been advantageous, for example in vegetation -rich environments. Similar Verhältnise length of the wings were to be found in present-day land-dwelling birds such as the Andean condor, while navy sailors, such as the wandering albatross, generally show rather long and slender wings.

Traditionally, large pterosaurs as extremely lightweight, which would have allowed a glider, which was significantly slower than today's birds. When a weight is assumed, which is comparable with that of today's birds and bats, this picture changes dramatically: Witton and Habib (2010) calculate that a 200-kilogram heavier Azhdarchide with a wingspan of 10 meters after the start for about two minutes with a powerful could maintain wing beat, in which the animal reaching speeds of over 100 km / h before the animal was transferred to a somewhat slower gliding. Such Azhdarchide was able to cover more than 16,000 km without any stopovers, more than any other animal.

Locomotion on the ground

Fossil footprints of previous and ongoing pterodactyls show that many species were significantly more competent in the locomotion on the ground than traditionally assumed. In Korea discovered Haenamichnus mentioned tracks are attributed to a very large representative of Azhdarchidae: The Hinterfußabdrücke measure 35 centimeters in length, which has an animal with a shoulder height of nearly three meters and a wingspan of about 10 meters. These footprints are currently the only ones that can be attributed to a particular pterosaur group; no other known group could have left footprints of this size. One of the consequences Shuts measures seven meters in length, making it the longest known track result of a pterosaur. This Shuts result shows that the long limbs of Azhdarchiden a fast and efficient locomotion on the ground allow: The track sequence is narrow, indicating what perpendicular under the body limbs, and the Hinterfußabdrücke overlap regularly previously left behind hand - prints. The toes were provided with fleshy pads, with claw marks are missing.

Ecology

Douglas Lawson, in 1975, in a report on the newly discovered pterosaur Quetzalcoatlus, the first hypothesis to the diets of Azhdarchiden on. Although at this time pterosaurs were generally considered to be fish eaters, Lawon argued that it could have been at Quetzalcoatlus is a scavenger that used its long neck to penetrate carcass. So träten the fossils of this genus into continental deposits far from the coast and had been found along with the bones of herbivorous sauropod dinosaur. Several later authors have criticized this idea; so the connection was too stiff to the sauropod fossils random in nature and the neck to penetrate carcasses can.

Since Lawson scavenger hypothesis numerous other hypotheses have been proposed. When Langston (1981 ) speculated that Quetzalcoatlus could have groped with his beak in the mud by invertebrates; buildings thereon would have of arthropods that were combined with the bone of the pterosaur found. Against this hypothesis was put forward that the connection with the trace fossils by chance, the neck is too stiff and the shape of the beak was inappropriate; also no evidence of pressure-sensitive Herb Czech bodies or similar structures in the jaw bones, which in many modern birds the detection of prey in the mud could find. Several authors suggested that Azhdarchiden waded through shallow waters to nachstellten there prey. The long legs and long neck and head support this thesis; However, the proportional little feet were not suitable for probably a wading on soft sediment. Still other authors took into account that some members of the group eaten fruits or less flying animals could have hunted in the air.

The majority of the studies represented the hypothesis that Azhdarchiden could have been fish eaters. So suspected Lev Nessov (1984 ) that Azhdarcho and other Azhdarchiden in flight or while swimming with their beaks durchflügten the water to zuzuschnappen in contact with prey. This diet can be found in today's scissor beaks and allows these birds to catch prey in murky waters. Critics noted that skimmers numerous adjustments to these very specialized diet show, such as an increased TMJ and very robust cervical vertebrae, which are not found in Azhdarchiden. Various authors suggested meanwhile that Azhdarchiden encountered in flight their beaks specifically into the water to capture fish, similar to today's gulls, terns and frigate birds. The long neck and skull would have allowed these pterodactyls to capture fish without the wings touched the water surface. Opponents of the hypothesis argue that the cervical spine was almost at a right angle to the longitudinal axis of the skull; Thus, the animals could not invest in a line at Crashing head and neck. In addition, the neck was too rigid, and the tip of the snout not bent downward as with many modern birds, the show this diet.

The hypothesis has been proposed recent Witton and Naish (2008). According to these researchers exceeded Azhdarchiden from dry terrain to opportunistically take small to medium sized vertebrates and large invertebrates and occasionally carrion, eggs or fruit. A similar diet is found in some present-day border birds, such as the authentics storks. As the researchers argue that the majority of Azhdarchiden fossils was discovered in river sediments, which came at home to deposit. Representative of the group seem to have thus frequented continental habitats, such as forest and bush landscapes and river valleys. The proportionally small feet, which were equipped with fleshy pads and only small claws would have been most effective on solid ground. The long legs were ideal for stepping through vegetation, which enables downward beak a simple reaching the bottom, and the long, stiff neck could have been used, among other things, to peek out from an elevated position for prey or around the head of to approach their prey before they are startled by the kicks of the pterosaur. Witton (2013 ) considers that some Azhdarchiden might have gone in groups in search of food because sometimes fossils of several individuals are found together. The largest Azhdarchiden occur in the late Cretaceous, as medium-sized carnivorous dinosaurs were conspicuously absent. Witton (2013 ) speculated, therefore, that Azhdarchiden might have at least partially occupied the ecological niche of medium-sized carnivores in the late Upper Cretaceous.