These are significant because bird fossils are very rare.

The team also uncovered some bird fossils, which are very rare.

It was also the first time an early bird fossil has been shown to contain preserved pheomelanosomes.

Other bird fossils include Dasornis, a genus of pseudotooth birds.

Osteornis is a generica term for bird fossil.

It has been the site of discovery of ancient bird fossils.

Thomas Huxley would make extensive use of both the horse and bird fossils in his advocacy of evolution.

Another curious element of Sitio Sierra is the large amount, and variety of bird fossils that cover the site.

Confuciusornis is the fifth oldest bird fossil, about 25 million years after Archaeopteryx.

Besides those of clams and other mollusks, quite a few bird fossils (which are generally rare) have been found in this geological formation.