Sixty-six million years ago, a marine creature, minding its own business at the bottom of a Cretaceous sea, munched on some sea lilies—then didn’t feel too great. Now, a fossil hunter in Denmark named Peter Bennicke has found the remains of this Cretaceous snack: fossilized vomit.

Self-proclaimed "fossil geek" Peter Bennicke was recently searching a beach at the Cliffs of Stevns in eastern Denmark when he came across a strange fossil in a large piece of chalk. He took the fragment to a museum,