Crocodiles and their ancestors have been roaming the Earth for 200 million years, rubbing shoulders (do crocodiles even have shoulders?) with the dinosaurs, the BBC reports.
Now researchers—in a study published this week in PLOS One—say they've discovered the world's oldest known crocodile eggs. The fossilized eggs are 152 million years old and were dug up during a years-long excavation in Portugal—with some of them found in dinosaur nests, strangely enough.
Researchers say it's unclear why the crocodile eggs were in dinosaur nests, but it seems "to suggest some form of biological relationship." The eggs were laid by members of a group of prehistoric crocodiles known as crocodylomorphs.
The Telegraph reports they appear to be from two different types of crocodylomorph. The newly discovered eggs are 40 million years older than the previous oldest known crocodile eggs and yet are strikingly similar to the eggs of modern crocodiles.
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One egg clutch contained 13 intact eggs, making it the most complete clutch of ancient crocodile eggs ever found. (It turns out dinosaur eggs hatched in a potentially troublesome way.)
This article originally appeared on Newser: Scientists Stumped by Crocodile Eggs in Dino Nests