Hey man, it’s a good start. I noticed your signature says to critique your T-rex head harshly, but I’m not going to do that. What I will say is even though it’s a nice start, it’s no where near time to render normal maps or mess with SSS or texturing. There’s not enough detail to begin that stage yet. Take these two images for instance:
Right now, the head looks like a toy, especially with that SSS. It’s quite plastic really. You need more sculpt in there, more folds, bumps and wrinkles. You need to try to get a scaly skin effect going around the mouth, and you need to define the brow moreso. The neck should have wrinkled skin, and the gums are just too thin for those teeth. While I could touch on even more, you should have enough right here to go with. You want to improve in your dinos, well, let’s see you revamp the good start you have here.
GL 
PS I have to agree with Owldude… the brow needs more refining and those eyes are too small. While we truly don’t know what a real T-rex looks like, Jurassic Park set a standard that all of us dino modelers must adhere to. We have some leeway, but it should look similar in the end.