Balaur is not considered a bird, but rather a theropod dinosaur. While birds are descendants of theropods, Balaur is not classified as a bird itself. This distinction is based on several factors, including its skeletal features and evolutionary lineage.
Firstly, Balaur is classified as a theropod dinosaur because of its anatomical characteristics. The bones of Balaur are shorter and heavier compared to those of basal paravians, a group that includes early birds and their closest relatives. These skeletal differences indicate that Balaur had a more robust and less bird-like body structure.
Additionally, Balaur existed during the late Cretaceous period, approximately 70 million years ago. This places it in a time period before the evolution of modern birds. While Balaur shares a common ancestor with birds, it is not directly ancestral to them.
Furthermore, Balaur lacks several key features that are characteristic of birds. Birds possess feathers, which are absent in Balaur. Feathers are a defining characteristic of birds and are not present in any known fossils of Balaur. Additionally, birds have a unique respiratory system that allows for efficient oxygen exchange during flight, which is not observed in Balaur.
In terms of evolutionary lineage, Balaur belongs to the group of theropod dinosaurs, which includes well-known species such as Tyrannosaurus rex and Velociraptor. Birds, on the other hand, belong to the group called Avialae, which includes all living birds and their extinct relatives. While Balaur and birds share a common ancestor, they diverged along separate evolutionary paths.
Balaur is not classified as a bird but rather as a theropod dinosaur. Its skeletal features, evolutionary timeline, and lack of bird-specific characteristics differentiate it from birds. Balaur represents an important piece of the evolutionary puzzle, shedding light on the diversity of life during the late Cretaceous period.