Pteranodon, illustration by Heinrich Harder ( 1916)
- Worldwide ( inter alia Santana Formation, Solnhofen, Jehol Group)
The Pterosaur ( Pterosauria ) are extinct reptiles that lived about the same time as the dinosaurs and eg. this belonged to the group of Ornithodira within the Archosauria. They were active to fly by their large, wing- like wing membranes as the first vertebrates capable. The later birds and bats developed their ability to fly independently in each case.
The earliest finds of pterodactyls go back to the lower Upper Triassic ( Carnian ) in front of about 228 million years ago. They were present on the earth to the great mass extinction at the turn of the Cretaceous- Paleogene ( Cretaceous-Tertiary boundary) about 65 million years.
In the pterodactyls two different types can be distinguished: The Long-tailed pterosaurs ( Rhamphorhynchoidea ), which are characterized by a long tail and relatively short metacarpals, were the earliest forms, and disappeared in the Upper Jurassic. The short-tailed pterosaurs ( Pterodactyloidea ) with no or only had a very short tail and long metacarpals, which appeared in the Middle Jurassic and became extinct at the end of the Cretaceous period. This classic division is now no longer used in the taxonomy, as the short-tailed pterosaurs descended from the long-tailed pterosaurs. The long-tailed pterosaurs are therefore for the purposes of phylogenetic systematics a paraphyletic group.
- 2.1 The Anatomy of Wings
- 2.2 The spine
- 2.3 The skull and teeth
Way of life
An important question arises regarding the way of life of the flight ability of pterosaurs. It is actually no doubt that just the small species could certainly actively fly very well. With the large pterosaurs of the Cretaceous period, it was the other hand, probably primarily for glider pilots who were like the birds of prey rely on the updraft, or dynamic glider that used different fast horizontal winds in the lee of the wave troughs like the albatrosses to wide with little energy as possible routes to get it over with. For a dynamic gliding speaks the maritime way of life, as there are no thermals above the sea, and the high aspect ratio of many species. But even these animals had at least out of the water to be able to actively and start to gain height.
Especially due to the high energy expenditure, which is necessary for flying, you go today usually assume that the animals were warm-blooded and hairy to a great extent. This is supported by the discovery of the hairy sordes pilosus ( " Haired Devil " ) and hair-like footprints in other pterosaur fossils from the Solnhofen limestone and the Posidonia Shale of wood grubs.
Because the hind legs were formed only very small at the pterodactyls, the question arises how the animals were able to move on land. To answer this question, two alternative theories are discussed. According to Kevin Padian and Jeremy Raynor, the animals used their legs like today's birds and were bipedal ( biped ). They attribute this to the fact that the legs are constructed similar to that of modern birds, and were probably used accordingly similar. David Unwin and Peter Wellhofer instead go on the assumption that the pterosaurs, four-legged ( quadruped ) went and used their arms while ( like today's vampire bats), the wing finger was taken to the rear. They assume here that the wing membranes also included with the hind legs. The latter theory is the currently preferred. Studies of the pelvic structure of Anhanguera and Campylognathoides have shown that pterosaurs could not ask directly under your body the hind legs and especially the large pterosaurs may have only very cumbersome travels alone on its hind legs. Sure you're in this regard but so far not.
It is possible also that different types used different solutions here. So it's easy to imagine one of the smaller long-tailed forms on its hind legs, but more difficult for the large and most forms of late Cretaceous period.
Diet, habitat and reproductive
The pterosaurs were probably consistently hunters and carnivores. Besides, the early long-tailed pterosaurs hunted sure especially after fish and squids and lived on seashores or other large bodies of water. One indication of this is the very long and fish trap-like teeth that could be perfectly used for packing and holding of fish. The animals probably lived in large colonies similar in today's breeding colonies of sea birds. Later small pterosaurs were, however, very probably also insects hunters. A very unusual pterosaur named Pterodaustro from South America had very long and extremely thin teeth, which were a trap. He hereby filtered seawater and fed on plankton like modern flamingos.
Although most fossils of pterosaurs so far come from habitats to larger bodies of water, it is now undisputed that many species also lived in Germany, such as forests, mountains and even deserts. The lack of fossil record is due to the very poor Fossilisierungsbedingungen these habitats and the very thin bone of the animals.
Pterosaurs were archosaurs, like all oviparous animals. A published in 2004 find of a fossil embryo from the early Cretaceous period, about 121 million years ago, which comes from the Liaoning Province of northeast China, this is impressive. The egg found was a little smaller than a chicken egg and contained a well-preserved skeleton, besides also impressions of skin and wing tissue could be seen. The at the animal that probably was close to hatching, existing wingspan of 27 centimeters will be considered by the discoverers as an indication that the juveniles were probably early developers who already fly shortly after hatching and feed themselves independently of their parents could.
The fact that pterosaurs lived together in colonies, on the other hand is primarily based on theoretical assumptions and on a Fund in the Atacama Desert in Chile, where many remains of young pterosaurs have been found in very small spaces.
The Anatomy of Wings
The most striking feature of the pterosaurs are the redesigned front legs to great wings that have the animals will allow both the glide and the active flight. Here, the wing membrane between the body of the animals and the arm with the greatly elongated fourth finger of the animals, corresponding to the small finger in man stretched on. The other three fingers formed claws out of the flight skin, the first finger was missing.
The wing bones of pterosaurs were hollow and very thin walls in general. They contained many air-filled spaces, so that the weight of the bones was not too high. By trabeculae especially the ends of the larger bones were strengthened. In general, only fragments of wing bones are found, for this reason, intact bone are extremely rare. The wing bones of the two pterosaurs forms differ significantly.
The wings of the long-tailed pterosaurs consists of a relatively short upper arm bone (humerus ) and a relatively short metacarpals. The four finger bones, however, are quite long. The claws also sit at very short metacarpals. The forearm is as in all vertebrates from two bones, the ulna ( ulna ) is slightly longer than the radius ( radius). In cross section, almost all the bone in the stem region are oval, heart-shaped as they are on the ends.
In contrast, both the humerus and the ulna massive and longer, the spoke is as long as the ulna, only less thick in the short-tailed pterodactyls. Especially the metacarpal bones are much longer than that of the earlier pterosaurs forms, while the fingers in relation to the other bones are correspondingly shorter. Even short-tailed pterosaurs had mostly four finger bones. The claws are very well trained and also end to prolonged metacarpal. The bone wall is thinner than that of the long-tailed pterosaurs and thickened at the end of the bones. The cross-section is hollow and triangular and oval at the end. Particularly striking these features are at the very large forms.
The wing itself consisted of a skin structure which has been reinforced by closely spaced fibers, the so-called Aktinofibrillen and so on the one hand for stability and on the other of the blade for a crack resistance ensured. These structures could be studied at the well-preserved flight hides some pterosaurs from the Santana Formation.
The spine of the pterosaur is quite different from the earlier reptiles and the flying lifestyle and the associated requirements adapted to the axial skeleton. In some areas it felt very much like the spine of the birds ( convergence ) with a pronounced shoulder region and a massive region in the pelvic area. The back was very short and allowed accordingly only a few movements, the longest range represented the cervical spine, accordingly, the individual finds most of vertebrae cervical vertebrae.
The cervical spine is very long in comparison with other vertebrates. The neck consists of eight vertebrae in the early pterosaurs, while some of the larger late forms have reduced the number to six. The first two vertebrae of this section, the Atlas and the Axis were mostly merged into a single vertebra. The bone wall of the vortex was thin and the interior consisted of a spongy bone beams with large air spaces. Cervical ribs did not exist under normal conditions.
The thoracic spine consisted of up to twelve vertebrae, most species had less. The first vertebrae were usually grown to a massive shoulder structure at the shoulder blades ( scapulae ) ansetzten. This formed in some species a long bone that extended over six to eight vertebrae.
The dorsal spine consisted of about six vertebrae and was very short, but compact. Like all other vertebrae they were also filled with an entablature, but also they charged side a large hole, which completely penetrated the bone. In most species, these vortices wore short ventral fins.
The sacral or lumbar spine was usually fused into a solid bone, which focused on the pelvic bone in a tight connection. In the early long-tailed pterosaurs, this structure was relatively easy in the short-tailed pterodactyls, it was but a single pelvic bone. In this area there were usually six to eight vertebrae.
The tail spine was very long at the long-tailed pterodactyls and could more than 35 caudal vertebrae exist. In some of these pterosaur fossils found at the end of the tail a sailing impression, this was probably used for navigation and stabilization in flight. In the short-tailed pterodactyls the number of caudal vertebrae was reduced to a small number.
The skull and teeth
The skulls of pterosaurs resembled like other parts of the skeleton of the birds, especially through the various savings and reductions that made the skull lighter. However, the main difference concerns the dentition, which was very well educated especially in the early pterodactyls. The most massive structures and thus those that occur most frequently among fossil record, were the jaw tips and the jaw attachment on the quadrate.
An important feature of pterosaurs is a ring of bone plates which lay around the eye and its biological sense so far could not be clearly established. He probably served as a pressure compensation element. Furthermore, the animals had like all other archosaurs a third cranial window in front of the eyes ( prefrontal window) while it had reduced the temporal window. Many of the short-tailed pterosaurs had high and long skull crests that have served, depending on the interpretation of sound reinforcement and / or the flight stabilization.
The teeth are very often get fossil, but there were, especially in the late Cretaceous period, a number of species which had no or only very small teeth. The earliest pterosaurs had mehrspitzige teeth (usually with three peaks: Tricuspide teeth), which were replaced at about Rhamphorhynchus of long and pointed teeth. These teeth were in the long and thin pines on the mouth edge. However, some of the long-tailed pterosaurs also had no teeth.
During the Upper Jurassic, the number of teeth decreased with the pterodactyls. Some species still retained teeth at the front end of the jaws, others lost all his teeth, forming a beak -like jaws arose. The large pterosaurs of the late Cretaceous consistently had no teeth.
How the dinosaurs included the pterosaurs to the animal groups that triggered a huge fascination at their first discovery. Fossils of pterosaurs among the first found fossils of terrestrial vertebrates in general and have been investigated in accordance with the early history of paleontology in the early 19th century. The first description of a pterosaur from the year 1784 by Cosimo Alessandro Collini. Particularly well preserved fossils from southern England and Germany made the pterosaurs popular both within the scientific community as well as the people. Among the first finds himself Dimorphodon macronyx, which was discovered by Mary Anning in the Liasformation at Lyme Regis, and Rhamphorhynchus and pterodactyl from the Late Jurassic, which were found in the Solnhofen were. The findings meant that they were described as a most wondrous creatures of the prehistoric world. The German naturalist Georg August 1831 Goldfuß took the view that these animals probably would look more as if they had sprung from the imagination because of nature.
During the 19th and 20th century the number of fossil finds increased, and especially the diversity of the group became more and more obvious. Especially the limestones in Solnhofen and Eichstätt turned out to be very rich deposits of fossil pterosaurs. So here the Rhamphorhynchus very well preserved longicephalus was discovered in 1839 as the first pterosaur with a long, full tail. In the same layers were discovered in addition also short-tailed animals must have lived at the same time obviously. In England, especially the Wealden formation was rich with fossils of animals which were first described by Gideon Mantell as birds (1822, 1827 and 1837) and their affiliation to recognized the pterodactyls Owen 1846. Seeley, it placed the genus Ornithocheirus. 1870 Othniel Charles Marsh discovered in Kansas remains of the giant Pteranodon and thus the first pterosaur skeleton in North America. 1895 led Felix Plieninger a subdivision of the pterosaurs in long-tailed pterosaurs and short-tailed pterosaurs, which was revised only in the last two decades by phylogenetic analyzes.
Also during the 20th century took to the fossil record and the known shapes. The classical sites were added further documenting a world-wide distribution of the animals. Today, some particularly rich sites are located in the Santana Formation in Brazil, Pakistan, Senegal and northern China.
The pterosaurs of the Triassic
The earliest pterosaurs come from the Upper Triassic and lived accordingly before about 228 million years ago. Most of the representatives of this period, however, only bone fragments have been found complete skulls or skeletons are extremely rare. The early types can be identified primarily on their teeth, which are equipped with multiple peaks. The teeth of later types have only one peak and are long oval. Furthermore, the bones of early pterosaurs massive and have a thicker outer layer while the interior has less freedom.
Pterosaurs from the Triassic:
- Incertae sedis Preondactylus
All pterosaurs of the Triassic and Early Jurassic had long tails, also the most early pterosaur characterized by very long teeth, such as Rhamphorhynchus from the Solnhofen limestone.
The skeleton probably the best preserved of an early pterosaur represents Eudimorphodon Ranzi Represents the copy comes from the limestone of Cene near the northern Italian city of Bergamo. In the area of the stomach even remnants of the last meal were found in the form of fish scales. Obviously, this type was a fish -eater.
The Eudimorphodontidae play at the beginning of the evolution of pterosaurs an essential role from them already developed in the Triassic, the first representatives of Dimorphodontidae and Rhamphorhynchidae. These two taxa are still present in the Jurassic period, while the Eudimorphodontidae have disappeared at the end of the Triassic.
The most and the most complete findings of the Triassic are from Italy: from the Zorzino limestone at Cene in Lombardy and the Preone valley in the Alps.
The pterosaurs of the Jurassic
In the Jurassic period occurred in the pterodactyls to major evolutionary changes. They spread out around the world and settled many different habitats. The long-tailed pterosaurs that time usually had long teeth, the narrowing down heavily to the top. In some species, the teeth were notched, but most had smooth teeth.
Pterosaur from the Jurassic (higher taxa ):
- Rhamphorhynchoidea Anurognathidae
The long-tailed pterosaurs disappeared about the middle of the Jura. They were replaced by the short-tailed pterosaurs or Pterodactyloidea at the beginning of the Jurassic developed from a subset of them. This had the tail greatly reduced and show in their evolution a shortening of the teeth and an extension of the metacarpal on flight skin -supporting fingers.
During the Jurassic, the pterosaurs developed into a highly successful group of vertebrates. In the early and middle Jurassic period exclusively from the already known in the Triassic Dimorphodontidae and Rhamphorhynchidae with the Scaphognathinae, Campylognathoides and Rhamphocephalidae other taxa of the long-tailed pterosaurs.
It was not until later in the Jura tailless short-tailed pterosaurs, represented mainly played by the Pterodactylidae, a major role. At this time it came to the largest number of species of pterosaurs as a whole, they settled in a variety of habitats in all parts of the world.
A very rich repository of pterosaurs of the Jurassic forms of Solnhofen in Eichstätt and Solnhofen, in which the Archaeopteryx was found. The conditions for fossilization in this material are very good, so that even some wing membranes and soft tissue impressions are received. Among the finds in these Solnhofen include the skeletons of Rhamphorhynchus and pterodactyl.
Also as an excellent reservoir of Jurassic Qaratai or Karatau mountains in Kazakhstan are considered. Here the obvious hairy sordes pilosus was with conserved wing membranes found for example.
The pterosaurs of the Cretaceous
During the Cretaceous period developed the biggest forms of pterosaurs, giant forms at the same time of the dinosaurs and other animal groups emerged ( plesiosaurs, mosasaurs, ichthyosaurs ). As already shown, it is in these pterodactyls exclusively to short-tailed pterosaurs.
Pterosaur from the Cretaceous (higher taxa ):
The large pterosaurs were there to be found anywhere in the world, however there were still smaller forms. These smaller pterosaurs were likely to be in direct competition with the newly developing birds, which spread rapidly at this time.
Until the 1970s, was Pteranodon from North America as the largest pterosaurs, its wingspan reaching about eight feet. He was by the discovery of Quetzalcoatlus (named after the Aztec god Quetzalcoatl, who was represented, inter alia, in the shape of a plumed serpent ) exceeded, which could have reached a wingspan of up to 12 meters by extrapolation of his skull measurements and a comparison with other pterodactyls.
A very important site for pterosaur fossils of the Upper Cretaceous is the Araripe Basin in Brazil and, above all, known as the Crato Formation and Santana Formation layers. From the area are very different pterosaurs, including about Anhanguera, Criorhynchus, Ornithocheirus, Tapejara, Thalassodromeus, Ludodactylus and Tupuxuara.
Another important archaeological site for pterosaurs of the Cretaceous period in China 's Xinjiang, where important dinosaur ( including some feathered dinosaurs) and mammal finds ( approximately Hadrocodium wui ) were made. Among the pterodactyls about Dsungaripterus originate wei and Noripterus complicidens from this region, which is particularly conspicuous by their powerful jaws. As in Solnhofen and in the Crato Formation, the findings draw from the Jehol Group in Liaoning by " soft-bodied " from. The Chinese species resemble both finds from Solnhofen and from Brazil. The recent finds from China have a similar, if not even more diversity than there suspect.
As a third -rich region of the pterosaurs Niobrara limestone and other rocks are in Texas and Kansas, where some of the largest of the previously known pterosaurs have been found, such as Pteranodon ingens and Quetzalcoatlus. The bones of these animals are often very fragile and were found widely scattered.
Evolution of the Pterosaur
The pterosaurs come from a very high probability of early archosaurs, which were also the ancestors of crocodiles and dinosaurs. The fossil record of the lineage of pterosaurs missing, according to this descent could only be detected by a feature comparison of the different groups of animals. The main indication of the cranial structure of the pterosaur can be viewed. This has as the other archosaurs a third cranial window in front of the eye ( Präorbitales window) and the vertex window ( parietal foramen ) is reduced. As further evidence for the assignment of the pterosaurs have typical Archosaurierzähne, and the fifth toe is reduced.
Within the archosaurs are the pterosaurs probably the sister group of the dinosaurs represent, both of which are placed together in the taxon Ornithodira due to the same structure of the ankles. However, the sister group relationship is not as well-founded and coherent common features are missing. The currently accepted family tree thus corresponds to the following graph:
Outgroup ( plesiosaurs, ichthyosaurs, lizards, snakes, and others)
Crocodylotarsi (among crocodiles ( Crocodylia ) )
Dinosaurs ( Dinosauria )
Pterosaur ( Pterosauria )
As the closest relative of pterosaurs and dinosaurs at the same time a fossil is discussed from the Scottish Lossiemouth. This animal, named as Scleromochlus taylori, informs both groups some anatomical features. Revealing it could be particularly important for the evolution of flight in pterosaurs, as it is assumed that Scleromochlus taylori was a good jumper, perhaps even possessed a precursor of the wing membranes of pterosaurs. In 1914, Huene wrote about Scleromochlus ". ... It was a parachuting animal, Which had skin duplications on the forelimbs, Perhaps so in other places" He assumed that the animal lived in the trees and they used it as a jumping point for his gliding ( arboreal hypothesis).
The theory of the evolution of the pterosaurs from Scleromochlus -like precursors by Michael Benton in 1999, the more options the way of life of Scleromochlus taylori is specified and is primarily provides a very detailed feature analysis of the animal. Unlike Huene he favors the Woodward in 1907 established theory that while Scleromochlus was a Springer, but did not use trees as a launching point, but a floor runner with good jumping ability was pronounced ( saltatory hypothesis). Thus, to have originated from this type of jumper the first flying pterosaurs. So far it is not clear which of the two theories applicable, exciting, however, is that for the evolution of flight, the same theories have been proposed in birds.
The classic dichotomy of pterosaurs was resolved by phylogenetic studies of the last 25 years. Accordingly, the short-tailed pterosaurs in fact constitute a natural systematic unit, but are embedded in the different groups that were previously grouped into the long-tailed pterosaurs. A number of families and other Untertaxa have been described, but these are usually poorly defined. Below is a cladogram of a possible inner system from a standard work by David M. Unwin is playing:
A complete system with all genres can be found at classification of pterosaurs.