If Noah took T-Rex on the ark, they were probably babies.
However the way I read the flood account, I don't know that Noah necessarily took a pair of every land dwelling animal that was on earth prior to the flood. God caused the animals to come to Noah. And it's possible that God decided to leave some animals out. Since Genesis was written by Moses well after the flood, the reference to "every" animal, may mean every animal that we now have, as opposed to those that were in existence then.
Seems to me that would include T-Rex, Brontosaurus, every other dinosaur.
That is why you can't debate science with a creationist, whenever asked for any proof about anything, they just throw out the whole miracle thing. How fair of an argument is that? Why even pretend to call it a science?