Origin of birds
Many scientists believe that the birds originated from small dinosaurs – terapods. The main thing here was the appearance of feathers – as a result, some running and climbing animals gained the ability to fly.
The first bird scientists believe archeopteryx, first discovered in 1861. Judging by its appearance, it looked like something between a reptile and a bird with a toothy beak, a long bony tail, and pronounced feathering. In recent years, the remains of other “feathered reptiles” have been found.
Bird’s feathers perform two important functions: warms the birds and helps them fly. Those feathers that serve for heating are usually shorter and softer, and those with which birds fly – the so-called flywheels – are larger and curved in the form of a fan. It is unlikely that the plumage of both species appeared in birds at the same time. The first they almost certainly outgrew the heat-shielding feathers, and after that, after millions
On the assurance of some paleontologists, some kind of feathers are found already in Longiskvama – a reptile that lived in the Triassic period, however, most scientists in this is not entirely sure. The most convincing proof of this is the presence of plumage, as such, in small theropods, whose petrified remains were recently discovered in China. On one of them, sinozaropteryx, there are obvious signs of short fluffy feathers in the form of a long scallop that extends along the neck and all the back. It was already a feathered dinosaur, but he obviously could not fly yet.
Sinosauropteryx appeared a little later than Archeopteryx, from which it follows that the former were not their direct descendants. Meanwhile, judging by the presence of the ancestors of flying birds with fluffy plumage, it is easy to imagine how they looked long before full plumage. But more importantly, not even this, but how the wings developed and, most importantly, why. According to one
This “mundane theory” was based on some characteristic features found in archeopteryx, for example, the extraordinary strength of the paws. However, according to most paleontologists, modern birds originated from reptiles that lived not on land, but on trees. With the development of exceptionally long feathers, such animals gained the ability to soar in the air, which allowed them to easily move through the wooded area, without going down to the ground. Well, in time, they learned to fly really – waving their wings. But in order to learn to soar, the reptiles took a long time. It was possible, for example, to achieve tselurosaurus and other reptiles; the same can be said for some modern lizards. Supporters of the “tree” theory consider this as direct evidence that the first birds began with the same.
To hover, a lot of effort is not necessary, but waving their wings – it’s not an easy thing. Over time, serious changes occurred in the anatomy of the first birds, due to which they learned not only to remain in the air for a long time, but also began to differ drastically from their ancestors – dinosaurs. In this sense, evolution has followed a completely different path. And as the development began, the first birds began to spend more and more time in the air. Thanks to the same changes, the birds got rid of excess weight. The bones of the first birds for the most part fused, due to which the skeleton of them slightly eased. Like their ancestors – theropods, the bones of the first birds were hollow, filled with air – over time air cavities expanded, especially towards the wings and paws. In addition, they widened their sternum, and strengthened the pectoral muscles that provided the flight, and also – a triangular fork, or an arch that supported the sternum during the flight. Similar anatomical changes were quite successful. In the Cretaceous period, birds literally flooded the Earth, especially as the time of the reptiles was approaching the fateful end. Therefore, the birds were the only surviving descendants of dinosaurs.
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