Pterosaur - Wikipedia. Pterosaurs (. They existed from the late Triassic to the end of the Cretaceous (2. Pterosaurs are the earliest vertebrates known to have evolved powered flight. Their wings were formed by a membrane of skin, muscle, and other tissues stretching from the ankles to a dramatically lengthened fourth finger. Many sported furry coats made up of hair- like filaments known as pycnofibers, which covered their bodies and parts of their wings. Pterosaurs spanned a wide range of adult sizes, from the very small anurognathids to the largest known flying creatures of all time, including Quetzalcoatlus and Hatzegopteryx. Pterosaurs are also colloquially referred to as pterodactyls, particularly in fiction and by journalists. Pterosaur bones were hollow and air- filled, like the bones of birds. A Google ingyenes szolgáltatása azonnal lefordítja a szavakat, kifejezéseket és weboldalakat a magyar és 100 további nyelv kombinációjában. Flashcard Machine - create, study and share online flash cards Infection is the invasion of an organism's body tissues by disease-causing agents, their multiplication, and the reaction of host tissues to these organisms and the. Pterosaur wings were formed by membranes of skin and other tissues. The primary membranes attached to the extremely long fourth finger of each arm and extended along. They had a keeled breastbone that was developed for the attachment of flight muscles and an enlarged brain that shows specialised features associated with flight. These are not to scale; the wingspan of Q. The primary membranes attached to the extremely long fourth finger of each arm and extended along the sides of the body to the ankles. While historically thought of as simple, leathery structures composed of skin, research has since shown that the wing membranes of pterosaurs were highly complex and dynamic structures suited to an active style of flight. The outer wings (from the tip to the elbow) were strengthened by closely spaced fibers called actinofibrils. The 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 first, called the propatagium (. This membrane may have incorporated the first three fingers of the hand, as evidenced in some specimens. 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 is not certain, as studies on Sordes 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 pterosaurs had a broader uro/cruropatagium, with pterodactyloids only having membranes running along the legs. 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. Some scientists, notably Matthew Wilkinson, have argued that the pteroid pointed forward, extending the forward membrane. The proximal carpals are fused together into a . 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. Fossils of the rhamphorhynchoid Sordes. Indeed, analysis of pterosaur limb proportions shows that there was considerable variation, possibly reflecting a variety of wing- plans. This feature likely evolved to lighten the skull for flight. The first and perhaps best known of these is the distinctive backward- pointing crest of some Pteranodon species, though a few pterosaurs, such as the tapejarids and Nyctosaurus, sported extremely large crests that often incorporated keratinous or other soft tissue extensions of the bony crest base. Since the 1. 99. 0s, 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. A fuzzy integument was first reported from a specimen of Scaphognathus crassirostris in 1. Goldfuss. Pycnofibers were not true hair as seen in mammals, but a unique structure that developed a similar appearance. Although, in some cases, actinofibrils (internal structural fibers) in the wing membrane have been mistaken for pycnofibers or true hair, some fossils, such as those of Sordes pilosus (which translates as . The coat thickness, and surface area covered, definitely varied by pterosaur species. The presence of pycnofibers (and the demands of flight) imply that pterosaurs were endothermic (warm- blooded). The absence of pycnofibers on pterosaur wings suggests that the coat did not have an aerodynamic function, lending support to the idea that pycnofibers evolved to aid pterosaur thermoregulation, as is common in warm- blooded animals, insulation being necessary to conserve the heat created by an endothermic metabolism. Kellner and colleagues in 2. Collini misinterpreted his specimen as a seagoing creature that used its long front limbs as paddles. They relegate the term . Furthermore, Darren Naish concluded that atmospheric differences between the present and the Mesozoic were not needed for the giant size of pterosaurs. Earlier suggestions were that pterosaurs were largely cold- blooded gliding animals, deriving warmth from the environment like modern lizards, rather than burning calories. In this case, it was unclear how the larger ones of enormous size, with an inefficient cold- blooded metabolism, could manage a bird- like takeoff strategy, using only the hind limbs to generate thrust for getting airborne. Later research shows them instead as being warm- blooded and having powerful flight muscles, and using the flight muscles for walking as quadrupeds. The replica was launched with a ground- based winch. It flew several times in 1. Smithsonian's IMAX film On the Wing. However, the model was not anatomically correct and embodied vertical and horizontal tail stabilizers that pterosaurs did not have. It also had a longer tail, changing the weight distribution. The presence of a subcutaneous air sac system in at least some pterodactyloids would have further reduced the density of the living animal. The flocculus is a brain region that integrates signals from joints, muscles, skin and balance organs. Birds have unusually large flocculi compared with other animals, but these only occupy between 1 and 2% of total brain mass. 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. 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 quadrupeds or as bipeds. In the 1. 98. 0s, paleontologist Kevin Padian suggested that smaller pterosaurs with longer hindlimbs, such as Dimorphodon, might have walked or even run bipedally, in addition to flying, like road runners. Footprints from azhdarchids and several unidentified species show that pterosaurs walked with an erect posture with their four limbs held almost vertically beneath the body, an energy- efficient stance used by most modern birds and mammals, rather than the sprawled limbs of modern reptiles. Furthermore, as a whole, azhdarchid front limbs were proportioned similarly to fast- running ungulate 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. Azhdarchid pterosaurs had relatively small feet compared to their body size and leg length, with foot length only about 2. This suggests that azhdarchids were better adapted to walking on dry, relatively solid ground. Pteranodon had slightly larger feet (4. Pterodactylus, 8. Pterodaustro), adapted to walking in soft muddy soil, similar to modern wading birds. In reality, however, the majority of pterosaurs are now thought to have been terrestrial carnivores or insectivores. One of the few groups that were never thought to be piscivores are the anurognathids; these were instead thought to be nocturnal, aerial insectivores, a view still maintained today. With highly flexible joints on the wing finger, a broad, triangular wing shape, large eyes and short tail, these pterosaurs were analogous to some of today's insectivorous bats, being capable of high manoeuvrability at relatively low speeds. It seems to have been a predator of small mammals and squamates, and possibly also preyed on large insects. Evidence for the latter lifestyle comes from the highly robust, . Species in the former category, including Carniadactylus and Eudimorphodon itself, were highly aerial animals and fast, agile flyers. The former was almost certainly insectivorous due to its small size; Eudimorphodon has been found with fish remains in its stomach, but as most carnivores or omnivores will also eat fish, its clear diet is uncertain. Meanwhile, the slender- winged species, such as Austriadactylus and Caviramus, were likely terrestrial/semiarboreal in habits. The dentition of Austriadactylus seems to be well- suited to eating small tetrapods. Caviramus has high bite forces, indicating an adaptation towards hard foods. It should be noted that all eudimorphodonts possessed well- developed molariform teeth and could chew their food, with Austriadactylus and Eudimorphodon having a pair of these molariform teeth developed into enlarged fangs. Rhamphorhynchids can be roughly classified into two categories.
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