Fossilized Eggs Connects Dinosaurs To Birds

These dinosaur eggs share similar characteristics to those from birds. (Photo : Universitat Autònoma de Barcel)

What's the closest living relative to dinosaurs? If you answered "chicken," then you're pretty much spot on. Today's birds are the closest living relatives of dinosaurs. In fact, birds in general are believed to have descended from dinosaurs and new evidence supports that. Scientists have uncovered dinosaur eggs with an odd, oval shape that could help shed more light on the evolutionary link between dinosaurs and birds.

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The eggs have an ovoid, asymmetrical shape, and support the working theory that birds and dinosaurs from the Cretaceous Period share a common ancestor.

The eggs have been named Sanfoka pyrenaica and were unearthed in the Montsec area of Lleida in Spain on either sides of the Terradet's pass. They have been dated to the upper Cretaceous Period between 70 and 83 million years ago.

The theropod eggs are unique in the sense that they share characteristics with bird eggs that are not found in other dinosaur eggs at the time.

The asymmetry of the eggs is what intrigued the researchers the most. Eggs from non-avian dinosaurs are usually symmetrical and elongated. Asymmetry in eggs can be associated with the physiology of birds. A bird's oviduct can only form one egg at a time, and the isthmus gives the egg membrane an asymmetrical shape. The wider end of the egg contains a bag of air so for the baby bird to breathe in the last stages of development.

The only other egg from the same time period that shows similar characteristics is from a primitive bird found in Argentina.

The study was conducted by Enric Vicens, a paleontologist from the Universitat Autònoma de Barcelona and paleontologist Nieves López Martínez, who passed away in December 2010.

The Cretaceous Period was a time where dinosaurs ruled the lands and many evolutionary paths opened up. For instance, ants, termites, bees, and even flowering plants began to be seen.