#guegoolithus

Guegoolithus is a fossil egg known the Maestrazgo Basin in Spain, dating back to the Barremian age of the Early Cretaceous. It is known from 400 fragments but no complete eggs have been found, with shells between .42 and 1.5 mm in thickness. The eggs were probably laid by an Ornithopod and were very similar in structure to Hadrosaur eggs, though hadrosaurs are not known from Europe and it is more likely they were laid by a close relative of hadrosaurs, such as a Styracosternan. 

Source:

https://en.wikipedia.org/wiki/Guegoolithus