Since the invention of the internal combustion engine, it has not been uncommon for broken turtle shells to turn up by the sides of highways, bashed by passing cars and trucks whose operators may not have even noticed. What is more striking is to find a version of this familiar story from 150 million years ago.

This much we know: One day toward the end of the Jurassic Period, a long-necked, long-tailed sauropod dinosaur about the size of an elephant lumbered over a tidal flat in what is now Switzerland, leaving footprints wider than beach balls.

Maybe it heard a crunch. Because much later, near these footprints , a team of paleontologists found a damaged carapace from an extinct sea turtle species called Plesiochelys bigleri halfway pressed into the sediment. They argue, in a paper soon to be published in the Swiss Journal of Geosciences, that animal was stepped on.

“The evidence is pretty clear,” said Daniel Marty, a paleontologist at the Natural History Museum in Basel, Switzerland, who participated in the study. “It’s kind of a funny thing, and it also shows that these two animals were in the same paleoenvironment.”