Origin and Evolution of Birds. Did they come from the Dinosaurs?

The origin and bird evolution Throughout history, it is one of the great enigmas that biologists and archaeologists have had to study, so this resulted in an agreement, which refers to the fact that birds evolved from the time of the dinosaurs. Find out all about the past of these species!

What were the first birds?

One of the first birds, or perhaps the oldest, was the one known as Archeopteryx Lithographica, which lived in European Germany approximately 150 million years ago, at the end of the Jurassic period. This primitive bird, which was of a size similar to that of the modern crow or chicken, had a body full of feathers, a long face like a beak and with teeth.

The forelimbs were transformed into wings with feathers, it had 3 fingers as claws and the chest muscles were weak, so it is concluded that it must not have been a good flier, but rather a climbing species that ascended through the mountains. tree trunks, using the claws of the hand and the tail, in addition to gliding to move between the trees and when hunting their prey.

It was in the XNUMXth century the first time that this relationship between dinosaurs and primitive birds was raised, as in the case of the popular bird Archeopteryx, which were found in Germany and have been considered the first birds in human history. . For scientists, birds are dinosaurs named as coelurosaurs and some of their relatives, were those that appeared in the Mesozoic period.

Although bird characteristics modern birds and this species are very different, as in the fact that the structure of this bird was more similar to that of the dinosaurs, with bent legs, rudimentary wings accompanied by claws, sharp teeth, a long tail and that they could even fly, however, today these characteristics are not present in current birds.

After Archeopteryx, other specimens appeared that were taken into account from the perspective of bird evolution, since these were approaching the external appearance of modern birds. It was then about 65 million years ago in the Cretaceous period that these animals began to experience more advanced changes, as happened with the following species:

• gansus: This fossil was found in China, it had more advanced bones and similar to the birds of these times.
• ichthyornis: These flying birds had a certain resemblance to seagulls, they were small, about the size of a pigeon, they had teeth and they lived in the regions of America.
• ambiortus: This fossil was found in Mongolia with keel tapeworm and carpus metacarpus, which is a trait very similar to modern birds.
• hesperonis: These belonged to the group of flightless birds and that they also had the habit of swimming, they lived in North America, they were aquatic with bulging feet and their main diet was based on fish.

evolution of birds

Birds are now thought to be descendants of the dinosaurs named theropods, the ancestor of birds was similar to the theropod named Deinonychus, which were found in the 60s, and this important finding was what convinced scientists and experts on the subject that birds descended from the dinosaurs.

In the 70s, the Yale University paleontologist John Ostrom was able to study the unheard-of similarities between the skeleton of theropods and that of birds. So according to the results obtained by this expert, the birds were descendants of theropods, which evolved over the years, since there were many theropods that had very large legs, short arms, with a very long and thick tail, that is to say They were very different from modern birds.

He concluded that both groups had a large number of characteristics and that theropod dinosaurs must be the direct ancestors of birds. In 1996, other paleontologists from China made a discovery that ended up confirming what Ostrom said, since they found a fossil of Sinosauropteryx, what were they feathered dinosaur and small theropods with short arms, their backs and tails were full of holes with fine filaments, that is, signs of feathers, which corresponds to a sighting of the bird evolution.

Later, on other occasions, hundreds of feathered theropods were found and several of these developed various types of feathers, some similar to those of modern birds and others with symmetrically arranged knobs, or on the other hand they had broad and resistant ataderas or broad blades, different of the feathers of any current bird specimen.

However, until recently it was thought that the plumage came from the theropod family, but in 2009 some scientists from China made the discovery that the Tianyulong was descendant of the dinosaurs, meaning they were not theropods. This discovery opens the possibility that the ancestors of the dinosaurs had feathers and could have lost them during their evolution.

There is currently agreement that the bird evolution It originated from a small theropod dinosaur that was carnivorous, and it is assumed that this was at some point in the Middle Jurassic, approximately more than 150 million years ago.

Traces of feathers have been found in some Chinese raptors, for which it has been concluded that the feathers that originally appeared were not for flight, but probably regulate the thermo-temperature and keep it a little higher than normal. the one that was in the environment, which means that they were warm-blooded animals, such as mammals and current descendants of the dinosaurs.

By obtaining feathers, the dinosaurs could not fly, so the old hypothesis that birds evolved from gliding animals is discarded, since raptors definitely did not have this type of customs, however, it is most likely that in addition From serving to keep warm, the feathers of the arms and hands could be used to hunt insects and get their food.

What was Deinonychus?

It is believed that the dinosaur with the scientific name Deinonychus was the closest relative to today's birds, since they were feathered dinosaurs currently extinct, which inhabited the earth approximately 110 million years ago in the North American territory.

This was a predatory animal with many characteristics similar to those of birds, such as; strong legs with claws, wings and feathers, with a respiratory, circulatory and digestive system very similar to that of birds, although this was a warm-blooded animal with characteristics also from reptiles, such as jaws with teeth.

Origin of Flight in Birds

At the end of the Mesozoic stage, the birds had already established themselves on earth, however, it was in the Cenozoic era that they had an extreme change, as evidenced by the large amounts of fossils that have been found until today. . Initially, the wings may have arisen due to the need that these species had to escape from their predators.

Birds have many similarities to the skeleton of dinosaurs, since the fossils of many of these have been found with their feathers well protected, although there were also dinosaurs that had long feathers and their arms in the form of wings, such as the Anchiornis and Microraptor.

There are new paleontological study techniques that have carried out a reconstruction of what is supposed to be the bird evolution, and it was concluded that the characteristics of these gradually emerged over millions of years, added to a large amount of evidence confirming that evolutionary transformations occur gradually.

Many fossil records of feathered dinosaurs have been found in China, and detailed records of the radical transformation of these species into delicate flying birds have been made.

https://www.youtube.com/watch?v=msZp83LjVp0

The number of bird species at the beginning of the Pleistocene era could be up to 21 thousand, however, due to the different climate changes, the formation of glaciers and the exchange of fauna between some continents, this number of birds was reduced. up to almost half. In addition, studies have been carried out on fossils of prehistoric birds from different species, which could establish that their extinction was unexpected.

According to some authors, the origin of the flight and the bird evolution It is related to the ability of some tree species to jump between trees, although others claim that the origin is linked to feathered dinosaurs. There are two hypotheses that talk about how was the evolution of the ability to fly in birds:

1. The first hypothesis is that the running dinosaurs began to use their wings to be able to balance and to hang from tree branches.
2. On the other hand, the second talks about how arboreal dinosaurs used them to control their jumps, avoid predators and propel themselves to capture their prey.

Which means that at first the wings were not used to fly, but at first they served to maintain balance and then help to avoid precipitous falls. When the dinosaurs became extinct, some of these species managed to survive that catastrophe and their offspring was the one that made possible the origin of the birds that are currently present throughout the planet earth.

Currently scientists and experts in this field do not know for sure the how or why of the wings, in addition to the fact that they can fly, however, they still continue to investigate and not only fossils, but also vertebrates such as bats and their flight adaptations. It should be noted that being able to fly is linked to some important situations.

Similar characteristics between Dinosaurs and Birds

Among the characteristics or adaptations of the birds that allowed them to facilitate the flight, are the following:

• Light bones and a variety of skeletal elements fused together.
• Reduction of the fibula and great development of the pectoral belt in relation to the movement of the wings.
• Arms transformed into wings and feathers.
• Tail reduction.
• loss of teeth
• Opposable toe, which allows them to cling to tree branches.
• Scaly feet.
• The skulls of both are attached to the first neck vertebra by a ball-shaped joint, the occipital condyle.
• They have a single bone in the middle ear.
• They have a lower jaw composed of 5 or 6 bones, these were replaced by beaks.

It should be noted that there is a much stronger relationship between dinosaurs and birds if we pay special attention to their skeleton, since most of the bone system has similarities, especially in areas such as the keel, which is essential in birds.

It is also amazing to know that the Carnivorous dinosaurs they had air sacs similar to those of birds, it is even believed that these prehistoric animals slept like many birds, as they also put their heads tucked under their limbs to keep warm.

On the other hand, both the behavior and the biological part of the dinosaurs leave evidence of the origin of birds, since both produce a kind of tissue rich in calcium that helps them produce the shell of their eggs.

Many dinosaur fossils that have been found had young in the process of incubating and small stones have also been found in their digestive systems that helped them in the digestive process, something similar to what the gizzard does in birds, in addition to the absence dentures early led parents to return food to their young, in order to feed them.

Bird Classification

The common and usual classification that can be useful to be able to group and identify these animals, especially modern birds, according to what is considered by many experts, are integrated into the group of tetrapods (animals with four limbs), of the breed Sauropsida, belonging to the subclass Diapsida, Infraclass Archosauromorpha, to finally incorporate them into the Archosaur side of the Archosaurs.

In the group of current birds, the Neornithes, we can find 2 subgroups which are very different, since some are very primitive and the others are very advanced, for example:

• Neognathae: It is a species of bird that has a more evolved neonatal palate, where its palatine and pterygoid bones are no longer united.
• paleognathae: They are birds that among their characteristics we can find a palaeognathic palate, which means that it is more primitive, like the ostrich, which is a running bird and has lost its ability to fly.

Anatomical Stability in the Evolution of Birds

The most authentic quality of birds is that their physical structure has not changed drastically, despite having emerged from thousands of different species, unlike what happens with other types of animals, where their body, wings, legs and physical appearance have presented some changes, although they are not so extreme.

In these species, the wings have hardly changed since the arrival of Archeopteryx, the only visible change being the atrophy of these limbs or different shapes and sizes, according to the different specializations of flight, such as speed, bioplaning, diving , among others

However, they have had changes of another type, such as in their size, plumage and habits, there are currently more than 40 thousand different species of birds that range from the smallest, as is the case of the hummingbird, to the largest. big as the ostrich.

With regards to bird evolution, we could say that dinosaurs have not become completely extinct, but that they live among us, they are present in our environment and right next to us, we can have them as pets in our homes, enchanting us with their beautiful sounds and company, such as canaries and cockatoos

While others, like the hen that allows us to taste the delicious and nutritious eggs, or the tasty and exquisite broiler chicken, which we savor in a roasting pan, breaded or in the multiple presentations that are offered to consumers today, that is to say that when we observe that checkered and scaly skin on the leg of a hen or a chicken, it is nothing more than a trace of the great and first ancestors of birds.

Evolution of the Dinosaurs

Recent investigations that were made on the incomplete bone system of a bird collected in the Antarctic continent, indicate that the genesis and bird evolution modern would have begun in the Mesozoic, which was dated approximately 72 million years ago in prehistory and was raised as part of the descendant of the Anseriformes, which are what we know today.

According to research carried out by expert scientists, birds emerged from a group of carnivorous and bipedal dinosaurs, that is, they walked on two legs and as more than 50 million years passed, they had changes such as their shrunken legs. The ancestors of birds also had new changes, such as feathers, spurs, and wings.

Theropods are a large family of dinosaurs that include specimens such as the Tyrannosaurus Rex, who had a height of approximately 14 and 15 meters, while their food was small reptiles and insects.

Flying Dinosaurs

Among the main and most studied flying dinosaurs, we can find the following:

• scaphognathus: This one lived on earth about 150 million years ago, it was almost a meter tall and its head was short, it ate meat and had 28 pieces of teeth, 18 in the upper jaw and 10 in the lower jaw.
• Pteranodon: These were one of the largest pterosaurs, they measured approximately 1.83 meters, they had weak and small legs, they did not have a tail, but they did have large wings. According to scientists, the pteranodon could have flown at speeds close to 48 kilometers per hour, so it is believed that it was an excellent flier, an ability that made it a predator, although it ate fish more than anything.
• Pterodactyl: It was one of the first species of short-tailed or tailless pterodactyloids, "pterodactyl" is the term used for reptiles that had wings, it is said that they lived until the end of the dinosaur era, but they were not really dinosaurs, but reptiles with wings. Studies show that these were excellent flyers and that thanks to their pointed teeth, they could have fed on fish, flying insects and land animals.

• Preondactylus: This was the smallest, it was approximately 30 centimeters long, its teeth were also tiny and it fed on small fish that it hunted out of the water. Its wings were short, measuring approximately 18 centimeters and thanks to its small size it could fly very quickly.

Descendants of the Dinosaurs

Many people ignore how much the dinosaurs meant in their passage through the planet, and we must highlight their great participation in the origin and bird evolution, since after its extinction when the meteorites fell, many birds were able to avoid them and survived, thus having the need to reproduce, and then create new species, like the birds we have today.

It is not currently known how many dinosaurs survived the extinction, but there are many other animals that are also descendants of the dinosaurs, such as some reptiles that still have strong armor.

There is a probability that the closest living relatives of birds, dinosaurs and pterosaurs are crocodiles and lizards, despite the fact that these animals do not currently have feathers, the discovery in lizards of the same gene involved in the formation of the feathers of the birds suggests that perhaps their ancestors did have them, now in reality the great unknown is how these animals lost their feathers.

Giant Prehistoric Birds

More than 55 million years ago, the Gastornis Giganteus existed, which could reach a height of 2.2 meters and was a bird that lost its ability to fly, had very large beaks and skulls.

Then, 24 million years ago in the Miocene and Pliocene era, there was a type of bird with similarities to vultures called Argentavis Magnificens, a species that could fly and average more than 7 meters, in addition to being able to weigh more of 75 kilograms. There were also the Teratornis Merriami, which lived in western North America and could reach over 4 meters in height.