This specimen of the odd-looking dinosaur Baryonyx was found in Surrey, United Kingdom, in 1983.
The 125-million-year-old creature was recently found to have a skull that functioned like that of a fish-eating crocodile, though the dinosaur's skull look like that of a meat-eater.
Some evidence, such as remnants of fish in the specimen's stomach, already pointed to a marine diet.
"I thought originally it might be a fish-eater, and [this study] has demonstrated that to be the case," said study co-author Angela Milner of the Natural History Museum in London.