Pterodactylus

Active flying vertebrates. Their wings are made of membranes made of skin, muscle, and other soft tissues, extending from the sides of the body to the extremely long fourth finger. [2] Earlier species had jaws full of long teeth and long tails; later species had greatly shortened tails, and some late species lacked teeth. Traces of filamentous structures have been found on the bodies and parts of the wings of some specimens, indicating that pterosaurs may have evolved hair. The bones are thin and hollow in the middle, with a particularly elongated first finger to support the membrane wings, short hind legs, a relatively short tail, and a relatively long head. These characteristics allow pterosaurs to glide in the air and on the sea, returning to land only to lay eggs. Pterosaurs are insectivorous animals with small teeth that feed on insects, and some also forage for fish. These characteristics together constitute the unique biological characteristics and ecological niche of pterosaurs

Mainly distributed in Europe, Asia, America, Africa and Australia

Pterodactylus (Quetzalcoatlus northropi), also known as the flying pterosaur, is one of the representative genera of the order Pterosauria and the first pterosaur to be named.

Wingspan: The wingspan of Quetzalcoatlus was 50 cm, and the wingspan of Pterodactylus was 2.4 meters.

Living period: Late Jurassic

Naming

In 1809, Georges Cuvier named this animal Ptero-dactyle. [9] In 1812, Soemmering named the same specimen Ornithocephalus antiquus. Since Cuvier named it earlier, Cuvier's naming had priority, so the name of this holotype specimen was Ptero-dactyle antiquus. In 1815, Constantine Samuel Rafinesque Latinized this name to become the current name Pterodactylus.

The first specimen of this famous reptile was found in 1784, making it the earliest pterosaur ever discovered. The name Pterodactylus means "lizard with winged fingers", and the English word "Pterodactylus" that represents its name is often mistakenly used as a synonym for the entire order Pterosaur.

It is an extinct reptile and vertebrate that can fly. The forelimbs of pterosaurs have become membranous wings, which are formed by the elongation of the fourth finger of the forelimb and connected to the membrane extending from the ventral side. The fifth finger has disappeared, and the remaining three fingers are very small, with claws at the front. The skeleton is hollow and light, the skull is flat, with many conical teeth, and the sternum is developed. Pterosaurs only have membranous wings. Although the wings are large, they cannot fly long distances because they have no bone support. The male has a small pelvis and a ridged skull, while the female has a large pelvis and a ridgeless skull.

The body structure of pterosaurs is compact, the chest cavity is small, and the tail is short, but its wings are long and have three tiny claws. The neck of the pterosaur was very developed to support its huge head and beak, but it did not have a crest on its beak. There are more than a dozen species of pterosaurs that have been identified, and they do not vary much in anatomy and size. The largest species ate fish, while the smallest species probably ate insects.

These giant pterosaurs were able to migrate very long distances, and their distribution was probably much wider than the few fossils found show.

Fossils were found in Europe (England, France, Germany), Africa (Tanzania), North America, South America, Europe, Africa, Asia, Australia, Xinjiang, Inner Mongolia, Liaoning, Hebei, Gansu, Sichuan, Shandong, Zhejiang and other places in China. Pterosaur fossils have been found in all continents, including Antarctica, worldwide. At least 60 genera of pterosaurs have been found, ranging from small birds to large pterosaurs with wingspans of more than 10 meters.

In 1784, Italian scientist Cosimo Alessandro Collini, then director of the Scientific Curiosities Collection of Karl Theodor, the Elector of Bavaria, discovered the first fossil of a pterodactyl in the Solnhofen Limestone in the Electorate of Bavaria (now Germany).

In 1817, a second specimen of a pterodactyl was discovered, also from the Solnhofen Limestone. This small specimen was named Ornithocephalus brevirostrus and, after several changes, is currently classified as an ancient pterodactyl. The short snout of this specimen is currently considered a characteristic of a juvenile individual.

A group of dinosaur fossils in Brazil that had been forgotten for 40 years have been confirmed to be a new species of pterosaur that lived in southern Brazil about 80 million years ago.

The world's first pterosaur embryo fossil was discovered in the Jehol Biota in western Liaoning, China by paleontologists Wang Xiaolin and Dr. Zhou Zhonghe. Fossils of pterodactyl fetuses that died before hatching have been found in China and Argentina. These fossils provide important information about the embryonic development of pterosaurs, which, like birds and other reptiles, lay eggs rather than live young. Especially about how they prepared to fly. By comparing these fossils with the embryos of birds and crocodiles before hatching, scientists have found evidence that pterosaurs can fly when they hatch. If this discovery is confirmed, it will mean that pterosaurs may be the first vertebrates on Earth that can fly at birth.

This discovery not only reveals the unique biological characteristics of pterosaurs, but also provides a new perspective for our understanding of the evolution and development of pterosaurs. Pterosaurs have characteristics such as a particularly long "ring finger" to support the wing membrane, which enables them to fly. This discovery further confirms the evolutionary uniqueness of pterosaurs and their important position in paleontology

Morphological characteristics

Pterosaurs are an order of ancient reptiles. It is a branch of reptiles that developed into the air. Pterosaurs have long heads, long necks, large eyes, and long and pointed beaks. There is a cortical membrane between the fourth finger of the forelimb and the side of the body, which can fly. The forelimbs of pterosaurs have become membranous wings, which are formed by the elongation of the fourth digit of the forelimb and the thin membrane extending from the ventral side. The fifth digit has disappeared, and the remaining three digits are very small with claws at the front. The skeleton is hollow and light, the skull is flat, and there are many conical teeth. The sternum is well developed. Pterosaurs only have membranous wings. Although the wings are large, they cannot fly long distances because they have no bones to support them. The male has a small pelvis and a ridged skull, while the female has a large pelvis and no ridged skull.

The largest pterosaur can reach 6 to 8 meters when its wings are spread. There are two fossils found in China: one is in the Karamay area of Junggar, Xinjiang, called Junggarosaurus, with a wingspan of 3.5 meters; the other is in Linhai, Zhejiang, called Linhai Pterosaur. Both are found in the Cretaceous period (137 million to 65 million years ago).

Pterosaurs are larger than other pterosaurs and have almost no teeth, while other pterosaurs have teeth. The typical pterosaur had a shorter tail than other pterosaurs, and a crest on its head. Some pterosaurs were about the size of birds, while others could grow as large as small airplanes. The largest pterosaurs had a wingspan of 39 feet (12 meters).

The structure of the wing membrane that supported pterosaur flight was completely different from the wing structure of later flying vertebrates such as birds and bats. The wing surface of pterosaurs is formed by a membrane, which is composed of skin, muscle, and other soft tissues. The wing membrane can be divided into three parts. The first part is the propatagium, which connects the wrist to the shoulder and is located at the front of the wing membrane. It is the first part that encounters the air during flight. Some fossil evidence shows that the propatagium is also connected between the first three fingers. The main part of the wing membrane is the brachiopatagium, which extends from the extremely long fourth finger to the sides of the body (or hind limbs). However, there is still controversy about where the brachiopatagium connects to the sides of the body and whether it connects to the hind limbs. Some pterosaurs have a membrane connecting the hind limbs, which may extend to the tail, called the uropatagium. Its membranes appear to be fully adapted for flight and gliding, but are not as flexible as those of bats or the wings of birds, and are relatively fragile. The body is solid, with long, thin hind legs, and its structure indicates that it is not adapted for vertical movement or resting, and it hangs on its hind legs when resting. The neck seems to be held vertically in flight, at right angles to the head and forward. The skull is light and strong, with most bones fused together; it has an elongated beak; the eyes are large, and like many birds, the eyeballs are reinforced by a series of bony plates (scleral rings) located on their walls.

Using computerized tomography scanning technology, a three-dimensional image of the pterosaur brain was created from the fossils. The image shows that the pterosaur's cerebellar lobes are quite developed, accounting for 7.5% of the brain mass, the highest proportion among the vertebrates known to date. In comparison, the cerebellar lobes of birds that are good at flying only account for 1% to 2% of their brain mass.

The largest pterosaur was Quetzalcoatlus (Quetzalcoatlus). The wingspan was 11 to 15 meters long, about the size of an airplane. The smallest arboreal pterosaur fossil, the hermit forest pterosaur, has a wingspan of only 25 cm, which is similar to the size of a swallow.

Pterosaurs are a very special type of reptile with unique skeletal structure characteristics.

The forelimbs of pterosaurs are highly degenerate, and the fourth finger is lengthened and thickened to become the flight wing finger. It is composed of four wing phalanges, without claws at the front end. Together with the forelimbs, it forms the solid leading edge of the flight wing, supporting and connecting the membrane of the side of the body and the hind limbs, forming a wing membrane that can fly and has similar wings to birds. The wrist of the pterosaur develops a unique wing bone that extends forward to the shoulder and supports the wing membrane. The first to third fingers grow on the outside of the wing membrane and become small hooked claws, and the fifth finger degenerates and disappears.

It has a slender snout. The mouths of many pterosaurs are covered with needle-like teeth; while some derived species have no teeth and have narrow beaks similar to modern birds, such as the Pterosauridae and the Mysopterygidae[29]. The beaks of some specimens preserve keratinous tissue.

Most archosaurs have several holes in front of their eyes; in pterosaurs, the nostrils are connected to the anterior orbital fenestra to form a large hole called the nasoantorbital fenestra. The anterior orbital fenestra may have served to reduce weight, aiding flight.[29]

Crown

Many pterosaurs had crests on their heads. The first pterosaur to be found with a crest was Pteranodon, which had a pointed crest pointing toward the back of the head. Some species, such as Archaeosaurids and Nocturna, had crests of unusual shape and large size, made of bone forked with keratin.

New discoveries and detailed studies since the 1990s have shown that pterosaurs generally had crests, which is different from previous views. Pterosaur crests are mostly, or even entirely, made of keratin, and are therefore rarely preserved during fossilization. Using ultraviolet imaging, scientists have shown that fossils of Pteranodon and Pterodactylus also had crests, which were not previously known. According to past theories, only derived pterosaurs had head crests; however, the Pteranodon and Austrian pterosaurs discovered in recent years also had head crests, confirming that some pterosaurs also had head crests.

Hair

No evidence of feathers has been found in pterosaurs, but at least some pterosaurs were covered in hair-like filaments, similar to mammalian hair, but not homologous. Pterosaur hair is different from mammalian hair, but is a unique structure, and the two are the result of convergent evolution. Although in some studies, the fibers on the wing membrane have been mistaken for hair, some fossils do have traces of filaments on the head and body, such as Sodersaurus and Jeholopterus. Pterosaur hair is not similar to the hair of modern bats, which is another example of convergent evolution. Pterosaurs evolved hair based on the need for flight, which also shows that pterosaurs were warm-blooded.

In the 2009 study of Jeholopterus, paleontologist Alexander Kellner created a special term for pterosaur hair, "Pycnofibre", which means dense filaments.

Although they lived at the same time as dinosaurs, pterosaurs were not dinosaurs; they formed a unique branch on the evolutionary tree. Pterosaurs are reptiles that fly into the blue sky and are sometimes mistaken for "flying dinosaurs". Pterosaurs originated in the late Triassic period about 215 million years ago and became extinct at the end of the Cretaceous period 65 million years ago. When dinosaurs dominated the land, pterosaurs controlled the sky.

The size and shape of individual pterosaurs vary greatly. The largest ones, such as the pterodactyl fossils discovered in Texas, USA in the 1970s, have a wingspan of about 16 meters and a width of about 1.5 meters longer than an F-16 fighter. The smallest ones are shaped like sparrows.

Flight

The flight mode, wing movement method, and take-off method of pterosaurs have not yet been determined in the paleontological community. Paleontologists Mark Witton and Mike Habib proposed a hypothesis about the take-off method of pterosaurs. When pterosaurs take off, they will put their bodies in a ready state, then use the strength of their limbs to push their bodies forward at the same time, and then spread their wings to fly, similar to the ejection method of a catapult. When pterosaurs fly in the sky, they can reach speeds of up to 120 kilometers per hour and fly several kilometers at a time.

Walking

The hip sockets of pterosaurs are slightly facing upward and sideways, and the femoral head is moderately bent inward, indicating that pterosaurs have a semi-upright gait. When they fly, the thighs may be raised parallel to the body, similar to modern gliding lizards. In the past, paleontologists had a major debate over whether pterosaurs moved on the ground in a quadrupedal or bipedal manner. In the 1980s, paleontologist Kevin Padian pointed out that small pterosaurs had longer hind limbs, such as Dimorphodon, and they may have walked and run on the ground in a bipedal manner, like modern roadrunners, in addition to flying. A large number of pterosaur footprint fossils have now been discovered, showing obvious footprints with four toes on the hind limbs and three toes on the forelimbs, which can prove that pterosaurs moved on the ground in a quadrupedal manner. Larger pterosaurs have smaller hind limbs and a large front half of the body, and it is generally believed that they used four limbs when moving on the ground.

Footprint fossils show that pterosaurs walked with their soles touching the ground, similar to humans and bears, both of which are plantigrade animals. Footprint fossils of the sphenopterid family show that at least some pterosaurs walked with their hind limbs upright, rather than with their hind limbs extended to the sides.

Recent studies have found that some pterosaurs (especially the pterodactyls) can walk and run smoothly. Compared with other pterosaurs, the forelimbs of the sphenopterids and ornithopods are quite long; the arm bones and metacarpals of the sphenopterids are particularly slender, and the proportions of their forelimbs are close to those of hoofed mammals that are good at running. Their hind limbs are not suitable for high-speed running, but their steps are larger than those of other pterosaurs. The sphenopterids may not be able to run, but they can walk quickly and efficiently.

Active time

In 2011, scientists compared the size of the scleral rings of several pterosaurs, modern birds and reptiles to infer their daily routines and active time. Pterodactylus, Digger, and Goblin are diurnal animals, while Combjaw, South Pterosaur, and Rhacophorus are nocturnal animals. Archaeotropheus is an animal with irregular activity. Its foraging and movement behaviors are not positively correlated with day and night, and it only rests for a short time. According to this research result, Combjaw and Rhacophorus may have a lifestyle similar to that of modern nocturnal seabirds, preying on fish at night; South Pterosaur may have a lifestyle similar to that of some Anseriformes, filtering small animals in the water at night. Combjaw, Rhacophorus, Digger, and Pterodactylus were found at the same time in the Solnhofen Limestone in Germany. They may have occupied different ecological niches, had different lifestyles and food sources.

Reproduction

A pterosaur egg was found in a quarry in Liaoning Province, China, and many famous feathered dinosaurs were also found at the same excavation site. The egg was flattened, but there was no sign of breaking, indicating that the egg had a leathery shell, like today's lizards. The embryo's wing membrane was well developed, indicating that pterosaurs could fly shortly after birth.

In 2007, a study on the structure and composition of pterosaur eggshells suggested that they may have buried their eggs in the soil, similar to modern crocodiles and turtles. For early pterosaurs, burying eggs in the soil to incubate can reduce the weight of the mother body, but it will limit the geographical environment in which pterosaurs can survive; another possibility is to place the eggs under the body until hatching, similar to the practice of some lizards, but most archosaurs do not use this method.

Several newly hatched juvenile individuals have been found, including pterodactyls, rhacophorids, comb jaws, and sphenopterids. The bones of these juveniles have shown a high degree of sclerosis, and the proportions of the wings are close to those of adults. In the early history of pterosaur research, juveniles and adults were often classified as different species of the same genus. Adult individuals and very young individuals, such as Pterodactylus, Rhacophorus, and Pterosaurus in Brazil, can be found in the Solnhofen limestone in Germany and the marine sediments in Brazil. This proves that these individuals may have fallen and drowned when they flew over the center of the lagoon. This also shows that these young individuals have the ability to fly.

When the wings have the ability to fly, the young individuals will leave the nest. Another possibility is that they only rely on the nutrients originally absorbed from the egg yolk to survive the first few days after hatching, and then start to forage alone.

Cause of extinction

As for the cause of the extinction of pterosaurs, some scientific experts believe that the frequent eruptions of volcanoes led to the extinction of pterosaurs through research. Some experts believe that pterosaurs may have evolved to the stage of warm-blooded animals. Due to the slow evolution speed and different degrees, they were eventually dominated by birds with fast evolution speed and high degree.

Traditional theory believes that competition from early birds led to the extinction of many pterosaurs. By the end of the Cretaceous period, only large pterosaurs were found; small pterosaurs had disappeared and their ecological niches were replaced by early birds. However, the lack of small pterosaurs in the fossil record may have more to do with the fragile nature of their skeletons and their difficulty in preservation than with bird biodiversity.