When I was about ten, I read in a book about several killer whales attacking big whales,
gripping whale's lower jaw, forcing mouth open so tongue could be eaten. I thought at
the time it might be untrue. But here is an excerpt from whale site suggesting it is true:

"no less than seven
gray whales were observed by researchers to
have been killed by orcas. In this photo Van
Sommeran gestures toward the dead whales
torn and broken mandible and the missing
tongue. Long parallel scratched on the whales
flukes and pectoral fins are also clearly
associated with orca predation. "