How did birds come about?

How did birds come about?
How did birds come about?
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How did birds come about? Dinosaurs, Archeopteryx, or therapods?

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“First, it turned out that Archeopteryx was not at all alone,” writes in his book “The Birth of Complexity. Evolutionary biology today: unexpected discoveries and new questions”famous biologist, popularizer of science Alexander Markov. Paleontologists have discovered many species that are close to Archeopteryx, that is, with the characteristics of both dinosaurs and birds. These creatures were called enanciornis ("antibirds") to emphasize that they may not be directly related to the birds that exist today. "Ornithization, or" opticization ", followed many parallel paths, and it is not so easy to understand which of the" transitional forms "gave rise to modern birds," the author continues.

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Scientists still doubt that Archeopteryx and its relatives (enanciornis) are the direct ancestors of modern birds. Although the former acquired a number of avian signs, no further "opticization" is observed behind it. But in large numbers, all kinds of heirs of carnivorous dinosaurs were found, which are close in features to enanciornis or some other bird-like animals.

Feathers did not immediately become an attribute of flight. The first feathers seem to have served for thermal insulation and resembled modern bird fluff. Later, they came in handy for attracting the opposite sex. And only then could they serve for planning from branch to branch, accelerating the run and, finally, flight.

Among other things, a few years ago, Chinese paleontologists dug up a giant bird-like dinosaur (called a gigantoraptor) that appears to be able to fly (given the length of its gliding feathers). The remains of the unearthed monster testified that it was 8 m long and 3.5 m high, but since, as scientists established, died in the 11th year of life, it could grow to a much larger size. Gigantoraptor lived in China in the Late Cretaceous period between 89, 3 and 65, 5 million years ago.

Alexander Markov: “As the Russian paleontologist E.N. Kurochkin, Archeopteryx today does not have a single “bird” trait that would not have been found in certain dinosaurs”.

Previously, these features included feathers, hooked processes on the ribs and a fork (fused clavicles). Meanwhile, many of the features that modern (fan-tailed) birds have, but are absent in dinosaurs, have not been found either in Archeopteryx or in its relatives.

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“Archeopteryx and its relatives, the enanciornis, are undoubtedly descended from dinosaurs,” Markov continues. - However, according to E.N. Kurochkin, it was a dead-end branch that died out at the end of the Cretaceous period along with the dinosaurs and left no descendants."

Kurochkin believes that the ancestors of modern birds should be sought in more ancient times. It is likely that birds do not come from feathered dinosaurs or from Archeopteryx and Enanciornis, but from earlier reptiles - thecodonts, who lived in the Late Triassic. Moreover, it is possible that the thecodonts were the ancestors of both dinosaurs and birds. That is, it may well be that the birds did not descend directly from dinosaurs, as is commonly believed, but were their close relatives - a parallel branch descended from thecodonts. Perhaps the bird line, if it came from the thecodonts, was not initially successful and began to actively develop only after the dead-end, but dominant in that era, branch of Enanciornis died out. It was then that the birds occupied the vacant ecological niche.

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The most suitable ancestor of birds among the Thecodonts today is an animal called Protoavis, which lived in the Late Triassic.Although the protoavis did not know how to fly at all and calmly moved on the ground, this animal showed the most important signs of birds, which are not found in Archeopteryx, Enanciornis, or other feathered lizards.

Despite this, most Western researchers do not share this point of view and still consider birds to be the direct descendants of enanciornis and similar animals.

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