User blog comment:BastionMonk/Jurassic Park IV raptors/@comment-5870856-20130425231354

I think that the raptors represent two subspecies of Deinonychus but they are mixed up with the Velociraptors since Deinonychus antirrhopus was briefly considered to be a Velociraptor. Just like the debate in real life.

Hammond thought Deinonychus didn't sound scary enough and redubbed them. He also plucked their feathers as I theorized in the comments for No feathers in JPIV.