London: A fossilised dinosaur egg found in Spain shares the same characteristics as that of birds` eggs and could be the "missing link" to prove their "common ancestor".
The egg fossil, which dates to about 80 million years, was found in Montsec, the Daily Mail reported Friday.
It is oval shaped and similar to a chicken egg, and has an "air bag" inside which birds today use to breathe in their last stages of development.
An analysis of the discovery was published in the journal Palaeontology.
The South Pyrenean area in Spain is rich in dinosaur egg sites, most of which correspond to sauropod eggs from the upper Cretaceous, dating back more than 70 million years ago.