Heart: Like with all species the heart is the most effective place to shoot the Utahraptor, one-shots are very, very effective with either ammo types for the 12GA Shotgun.
Brain: Not particularly effective for the Utahraptors, if you do want to go for the brain make sure to aim right at the back of its head, around about the eye.
Lungs/Intestines: With the small size of the Utahraptor and its small amount of health, if you have a small amount of ammo a shot to the lungs or intestines will ensure that the raptor bleeds, meaning if you can avoid it for a small amount of time, it will probably flee and in most cases, drop dead about 40 metres away from you.