The blue whale is not only the largest animal alive today, it is the largest one that has ever lived. Now, analysis of a fossil found on the shore of an Italian lake hints at when, and perhaps how, the blue whale became such a behemoth.

The beast’s very large skull, described today in the journal Biology Letters, confirms that this ancient blue whale is the largest known in the fossil record, reaching a whopping 85 feet long. That’s just shy of the largest modern blue whales on record, which reach up to a hundred feet. Perhaps even more surprising to scientists, though, is the fact that a whale of this size swam the seas around 1.5 million years