Since 1861, 12 Archaeopteryx fossils have been found in Germany. The body structure of this animal is "half like a bird and half like a reptile": the distribution and structure of feathers are different from those of familiar birds. For example, the tail bone is very long, there are teeth in the mouth, and sharp claws remain on the wings. These characteristics are more similar to reptiles. So from the beginning, Archaeopteryx was identified as an excessive type of reptile like bird evolution. For more than 100 years, scientists have been accustomed to regard it as the most important transitional organism supporting Darwin's theory of evolution.
So why is it the most primitive bird?
To answer this question, we must first answer what is a bird. This is not difficult to answer. Birds have feathers and can fly. The difference between birds and other animals is clear at a glance. Archaeopteryx has feathers, but can it fly? How high can you fly? Although there is still debate on this, for a long time, most scientists still believe that no matter how good the flight ability of Archaeopteryx is, since it has the unique feathers of birds, it is also possible to count it as the oldest bird. Moreover, one of the most important principles of classification and naming is "Convention", and the purpose is to communicate. Here, there are no other birds older than Archaeopteryx, even in the same period. Therefore, for more than 100 years, Archaeopteryx's status as the earliest ancestor of birds has not been really challenged.
In 2011, Chinese Dinosaur scientist Xu Xing published an article in the journal Nature. Based on the discovery and analysis of new fossils, he believes that Archaeopteryx is not the ancestor of birds, but a feathered dinosaur closest to ornithosaurus. This article represents the strongest challenge to the status of Archaeopteryx in recent years. Is the position of the ancestor of birds to be shaken for more than 100 years? The scientists' reactions were inconsistent. At the end of 2011, some foreign scholars put forward different opinions on this. They used different analysis methods and concluded that Archaeopteryx is still the earliest ancestor of birds.
In fact, since the 1990s, with the discovery of more and more feathered dinosaur fossils in China, feather as a symbol of birds has become doubtful. Moreover, many skeletal features that used to be considered unique to birds have also been found in dinosaurs, so the boundary between birds and dinosaurs is no longer as clear as before.
Is Archaeopteryx still the earliest ancestor of birds? Perhaps today we can't provide a very positive answer, because science often makes progress in constant debate. It is believed that with the progress of more research work, scientists can finally reach a more consensus.