First you have to crack the egg by jumping on it. After that, hit its tail a couple of times and that should destroy that dinosaur.
Ok I know everone here is very knowledgeable and helpful so here goes: I'm stuck on a tiny planet with that dinosaur that is half covered in an egg. I need to know what to do, I have thrown stars at those flowers and they have bloomed but nothing else is happening. I will post some pics to help explain what I am talking about.
If you can help me i will rep you. =)