I’m going with dolphin as well.
Dolphins are predators.
The molars on this scull look to belong to a herbivore, or omnivore.
I think you are mixing terminology. You can be a predator and be an omnivore.
Dolphins are predators, but then again, so are bears that have omnivore teeth. What would set dolphins aside here is that they are "obligate carnivores." Dolphins differ from their terrestrial obligate carnivores in that they have all (virtually uniform) conical teeth, unlike say, cats, that have shearing teeth that are not uniform throughout the mouth.
Never mind the blowhole missing from this "dolphin" skull, LOL.