At birds, as well as all groups of living beings, did not appear on the planet the way they are today. Several evolutionary factors acted until the current forms were established. To assess these changes, the paleontological study is essential, as it provides information about the ancestry of each species.
O fossiliferous record of birds is quite incomplete, which hinders, in a way, the in-depth knowledge about the origin of these animals. The main problem with the record is the fossilization process, which is made difficult due to the presence of pneumatic bones and aerial habitat, which helps in the dispersion of mortal remains. However, despite the difficulty, several studies try to understand the evolution of this vertebrate group.
Currently, it is believed that, due to some similarities, birds are derived from a lineage of Therapoda dinosaurs. Among the similarities between these groups, we can highlight the elongated and mobile neck, the presence of three toes facing forwards and one backwards, and pneumatic bones. Furthermore, the presence of the well-known “lucky bone” and the fusion of the sternum are characteristics shared between birds and a specific group of Therapoda, the coelosaurus.
Some scholars believe, however, that the Crocodylomorpha or the Mammalia are sister groups to birds, however there is a lack of paleontological evidence for this fact. Therefore, the most accepted theory is that birds constitute a monophyletic group of tetrapods, which has some Coelurosauria dinosaurs as a sister group.
One of the most remarkable discoveries about the bird evolution it happened in 1996, when the first occurrence of a feathered dinosaur was recorded. Currently, several species of coelosaurus are known that have structures similar to feathers, which helps to confirm the theory of evolution of birds from this group of dinosaurs. However, studies show that initially these structures were not used for flight, appearing well before the development of this capability. Some researchers suggest they may have been used initially for social interaction.
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The most primitive bird that has been recorded is the Archeopteryx, which went extinct approximately 150 million years ago, at the end of the Jurassic. This genus had a feather arrangement very similar to that of today's birds. adapted for flight. This animal probably took flight running and flapping its wings, a behavior seen in current species.
In the 1990s, several other bird fossils were discovered, showing the emergence of a large number of species during the Mesozoic era, when this group had its origin. Since that era, several species have emerged and today we have a very large group of birds, which have about 10,000 species in the world.
Curiosity: There are still controversies regarding the classification of Archeopteryx as being the first bird or not. According to some researchers, the Archeopteryx it would just be another dinosaur and species like the Aurornis xui, which lived 10 million years earlier, could be considered the first species in this group. This is a classic problem in paleontology, as studies are based on fossil records, which are usually incomplete. Therefore, it is essential that studies in the area continue to be carried out so that definitive conclusions can be reached.
By Ma. Vanessa dos Santos
Would you like to reference this text in a school or academic work? Look:
SANTOS, Vanessa Sardinha dos. "Evolutionary history of birds"; Brazil School. Available in: https://brasilescola.uol.com.br/biologia/historia-evolutiva-das-aves.htm. Accessed on June 27, 2021.
