The world's oldest known crocodile eggs laid some 152 million years ago have been discovered in the cliffs of Portugal.
The remarkably well preserved eggs give an insight into the "mother croc" that laid them, researchers said.
They are similar to the eggs of modern crocodiles, suggesting crocodile eggs have changed little in shape in the last 150 million years.
Palaeontologists say the prehistoric crocodile ancestor would have spanned two metres, based on the size of the larger eggs.
"The fact that they are from the Late Jurassic makes these eggs the oldest crocodilian eggs known so far," said Joao Russo of Universidade Nova de Lisboa, Portugal.
"This new discovery from Portugal extends the knowledge of this type of egg by approximately 40 million years," said Russo.
Crocodilians arose some 200 million years ago, when they prowled the land with early dinosaurs.
The eggs were laid by a group called crocodylomorphs, close relatives of "true" crocodiles, 'BBC News' reported.
"The fossil record tells us that crocodiles and their relatives (forming the larger group of crocodylomorphs) were much more diverse in the past, with different feeding habits, ecological niche distribution or morphology," Russo added.
The eggs were found over a number of years during excavations of a dinosaur nest near the village of Lourinha, north of Lisbon. They were found in several clutches and appear to be of two different types.