You may have heard the theory that birds are descended from dinosaurs. In other words, the colorful and singing birds that brighten our days have their ancestors in the ancient dinosaurs.
The reality is that many experts on the subject claim that there is sufficient evidence to ensure that birds are descended from dinosaurs. On the other hand, some theories claim that dinosaurs became extinct from the face of the planet many millions of years ago.
However, certain fossil evidence suggests that dinosaurs did not really disappear from the earth, but followed an evolutionary process that turned them, millions of years later, into the birds that populate the planet.
For this reason, paleontologists actually speak of the extinction of non-avian dinosaurs, that is, dinosaurs that are not ancestors of birds.
Why birds are said to be descended from dinosaurs
Some researchers have made discoveries that have proven the theory that birds are descended from dinosaurs. Certain characteristics of birds are similar to those of dinosaurs.
The weight of each of these arguments is debated in the scientific community. However, the fact that evidence is accumulating implies that this idea is accepted in the scientific community; it is the details that are under discussion.
- Birds have in common with dinosaurs a pectoral bone, the furcula. It’s about that little bone that we usually call the wish bone. It is only possessed by birds and theropod dinosaurs, and is formed by the fusion of the two clavicles.
- Feathers are another element that birds have in common with dinosaurs. The dinosaurs known as Manirraptors are commonly accepted as ancestors of birds and had feathered arms and tails. Since these animals did not fly, it is believed that the feathers served to protect them from the cold, like the fur of land mammals.
- Some dinosaur fossils have skeletons similar to those of birds. That is, light and hollow bones, with long, slender legs like those of many birds living on Earth today.
- The lungs and heart of some ancient dinosaurs are very similar to those of present-day birds. This provides scientists with a more accurate basis for their assertion that birds are descended from dinosaurs.
- Many birds today use stones or gastroliths to aid in the crushing of food within the digestive tract. Evidence of gastroliths has been found in certain dinosaur fossils such as theropods and sauropodomorphs.
The extinction of non-avian dinosaurs
According to a theory proposed in 1980 and now considered accepted, 66 million years ago the non-avian dinosaurs were extinguished from the face of the Earth by the collision of an asteroid. This extinction, known as the Cretaceous-Paleogene extinction, involved the disappearance of 3/4 of plant and animal life.
However, evidence reveals that avian dinosaurs, other reptiles and the ancestors of mammals managed to survive this extinction. It is believed that the reason for this is that they were probably small animals, which did not need much food to survive.
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