Pterosaur

All the pterosaur and other flying reptiles were flourished during the period of Triassic, Jurassic and Cretaceous periods of the Mesozoic Era. These were about 252.2 million to 66 million years ago. Generally, the pterosaurs are not dinosaurs. But archosaurs of both species may be ruling reptiles, that are grouped into birds and crocodiles.  It is to be noted that, the pterosaurs were not the first reptiles that are capable to fly. But they were the first vertebrates to fly.  

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Classifications of Pterosaur 

The pterosaurs are classified into two major groups. Rhamphorhynchoidea is a species of pterosaurs, which lived about 161 million to 146 million years ago during the Late Jurassic Epoch. The Rhamphorhynchoidea are typified by relatively long tails, long fifth toes with sharply pointed teeth, and only slightly elongated wing metacarpals, which looks like palm bones.  Usually, the Rhamphorhynchoids were the first pterosaurs, which was recognized from the deposits from the Late Triassic Epoch. The Triassic Epoch period falls between 229 million to 200 million years ago. The genera of Rhamphorhynchoidea includes  Eudimorphodon and Peteinosaurus, both of their deposits were found in the Italian Triassic deposits. The wingspans of the pterosaurs have wingspans less than 1 metres. The Dimorphodon was a genus of a medium-sized pterosaur, which were from the Early Jurassic of England. The length of the species is about 1.5 metres from wingtip to wingtip. 

According to the study, the Rhamphorhynchus is the kind of pterosaurs, that was from the Late Jurassic Epoch period. And the wingspan of Rhamphorhynchus is about 1 metre. The Rhamphorhynchoidea is an artificial grouping of primitive forms that are more closely related to the other major group of pterosaurs, the Pterodactyloidea. Usually, the Pterodactyloids appeared in from Middle Jurassic and survived still the end of the Cretaceous. The entire Rhamphorhynchus are the earlier form of pterosaurs, which are extinct. 

The Kryptodrakon progenitor is the oldest known pterodactyloid, their fossil dates show the information of about 163 million years ago.  The fossil data of  Kryptodrakon progenitor are discovered from northwestern China, which was so far from the sea during Jurassic times. These flying reptiles provided strong evidence about pterodactyloid, which are evolved in landlocked environments rather than in marine settings. During the earliest Late Jurassic pterodactyloid is Pterodactylus, there were numerous individuals which are known from Solnhofen Limestone of Bavaria, Germany. Pteranodon can grow up to the length of about  7 metres, which was also known as pterodactyloid. 

Lacusovagus belongs to the family Chaoyangopteridae. These belong to the group of toothless pterodactyloids. The Lacusovagus species are known from a single fossilized skull, which was discovered from the Cretaceous rocks in Brazil. The average wingspan of the Lacusovagus is about 5 metres and they were the only member of Chaoyangopteridae, which was found outside China. 

As per the study of Darwinopterus modularis,  the researchers from Tiaojishan Formation in Liaoning Province, China possessed elements of both basal and more advanced pterosaurs. The Darwinopterus modularis has occupied the earth during the Jurassic Period, which was about 160 million years ago. The crow-size of pterosaur possessed a head and neck characteristic of the more advanced pterodactyloids. The existing skeletal features of the pterosaurs are similar to the rhamphorhynchoid pterosaurs. As per the research, the scientists found that the unique body design of the Darwinopterus body is evidence for many modular evolutions. The concept regarding Darwinopterus was built around the idea that natural selection can focus on certain groups of related physical structures, such as those that occur in the head and neck, while neglecting or acting more slowly on other groups of structures.

Still, no pterosaur remains in the world. As per the study, the most recent specimen of species were found on the Cretaceous. The ecological characteristics of the pterosaurs were taken over by the birds.

Physical Appearance of Pterosaur

The ancestors of the Pterosaur are the bipedal gait, which uses their only two legs for walking. They also used their freed forelimbs for flying. The birds and pterosaurs have limbs which are evolved as wings. The pterosaurs do not have feathers, but they have a well-developed wing surface by the membrane of skin similar to the bats. The bat membrane will have the support of all the fingers except the thumb. In pterosaurs have the membrane, which was attached solely to the elongated fourth finger. The first three fingers of the pterosaurs were slender, clawed, clutching structures. While the pterosaur was not flying, the finger and membrane were extended and remains towards their back along the sides.  In addition to the main flight membrane, other accessory membranes will stretch between their shoulder and wrist reduced turbulence on the wing. The appearance of the pterosaur wings was well adapted for flying. The pterosaurs wings have an embedded system of fine, long, keratinous fibres, which ran parallel to one another like the feather shafts of birds. The entire arrangement enhanced strength and manoeuvrability while the largest pterosaur flying.

The body of the largest flying dinosaur was compact and their hind legs were long and slender, like birds, which will easily support the animal to land after the flight. The forelimbs of the pterosaurs had forelimbs of considerable size, the bones on forelimbs had hollow bones and thin walls, through which the weight of forelimbs can keep low.  The skull of the pterosaur had a long, strong and slender beak. They have component bones fused with beaks of pterosaur. The eyes of the largest pterosaur were large and their eyeballs were reinforced by a series of bony plates. 

The posture and locomotion of the largest flying dinosaur on the ground vary depends on the time. Some species of this family are bipedal, but other species walked on their four legs. The Rhamphorhynchus was a kind of pterosaurs, which walked using a  plantigrade style, which means they were walking with the whole foot touching the ground. Other species also employed for digitigrade stance, which means they are walking on the toes without the rear of the foot touching the ground. Several other specimens of pterosaurs were had webbed feet, which may not suitable for swimming. The pterosaur faced many challenges associated with balancing their large heavy head, which was far away from their centre of mass. Pterosaurs were facing more trouble, awkward and difficult for floating and paddling. Webbed feet of pterosaurs can be used to prevent pterosaurs from sinking into the muddy ground.

The brains of pterosaurs were large and are apparent structure while comparing to other birds. The largest pterosaur had great sight rather than smell to have been the dominant sense. Still many sediments of pterosaurs were found in the bodies of waters and little sediments were exist in the diversity of forests or plains. 

The diet plan of pterosaurs may vary from species to species. Some pterosaurs, such as Pterodaustro had beaks with hundreds of fine needle-like teeth, which were used for straining plankton. Other species like Cearadactylus, have large teeth that were spread over outward slightly, which will help them for capturing fish and other land animals. Other genera, namely Eudimorphodon and Rhamphorhynchus, have been found with fish, which remains with their abdominal cavities.

Reproduction and Life History of Pterosaur 

The fossils of the pterodactyloid juvenile are found in the Solnhofen Limestone. Only a few data are leftover about the pterosaur reproductions. Many researchers believe that the Pterosaur may be reproduced through laying eggs like dinosaurs. But the fossils for such reproductions are rare. The first pterosaur egg was found in the quarries of Liaoning, where they yielded feathered dinosaurs. The eggs of pterosaurs were squashed flat with no signs of cracking, so evidently, the eggs had leathery shells, as in modern lizards. The Darwinopterus species eggs had a leathery shell, which looks like modern reptiles.  

In 2014, the  Hamipterus tianshanensis species five unflattened eggs were found in an Early Cretaceous deposit in northwest China. While examining the shells of pterosaurs eggs under the scanning electron microscopy showed the presence of a thin calcareous eggshell layer with a membrane underneath. As per the study in 2017, the study of pterosaur eggshell structure and chemistry shows that the pterosaurs buried their eggs, like modern crocodiles and turtles. The burying of eggs has beneficial to the early evolution of pterosaurs. The eggs allow them for more weight-reducing adaptations. The method of reproduction is limited by various environmental factors. Many eggs of pterosaurs also need to face ecological competition to survive. From the specimen Darwinopterus, it was observed that they have pairs of functional ovaries as opposed to the single functional ovary in pterosaur. Here, the dismissing the functional ovaries as a requirement for powered flight.

Wing membranes have special characteristics to preserve and develop pterosaur embryos. So that the young pterosaurs were ready to fly soon after birth. According to the tomography steady the fossils, the young pterosaurs from Hamipterus eggs had well-developed thigh bones for walking, but weak chests for flight. The existing fossils of pterosaurs are only a few days old species found, which represent several pterosaur families includes pterodactylids, rhamphorhynchids, ctenochasmatids and azhdarchids. All preserve bones of Pterosaur will show a relatively high degree of hardening for their age, and wing proportions similar to adults.

Researchers initially considered pterosaur flaplings as an adult and later they are placed in separate species in the past. Flapling are found normally in the same sediments as adults and juveniles of the same species, such as the Pterodactylus and Rhamphorhynchus flaplings found in the Solnhofen limestone of Germany, and Pterodaustro flaplings from Argentina. All the flapping are found deep in an aquatic environment far from shore. 

Scientists are also found that the largest flying dinosaur species may have the practice of having parental care for their parents. The young flaplings can fly as soon as they emerged from the eggs. As per experts Christopher Bennett and David Unwin, numerous flaplings were found in environments far from nests along with the adults. They also concluded that the young peoples were dependent on their parents for a relatively short period of time, during a period of rapid growth while the wings grew long enough to fly, and then left the nest to fend for themselves, possibly within days of hatching. Like modern reptiles, the stored yolk products provide essential nutrients for the young pterosaur. As per the fossils of Hamipterus nests, Both the male and female pterosaurs together will preserve their eggs similar to that of modern seabird colonies. The young pterosaurs do not have well-developed chests, so they required huge parental care during the initial days. 

As per the study, the growth rates of pterosaurs varied depends on their growth rate. The average growth of long-tailed pterosaurs, such as Rhamphorhynchus can grow faster than the growth rate of alligators. Their growth rate during the first year of life is about 130% to 173%. 

Growth in the tupandactylus species may be slowed after attaining sexual maturity. Further, it would have taken more than three years for Rhamphorhynchus to attain maximum size. The large pterodactyloid pterosaurs, such as Pteranodon will attain their maturity as adults during the first year of their life.