Yes, there are. Ancient Greek sources reference the finding of huge bones in several locations - off the top of my head in remembering perhaps Macedonia and/or Thessaly, Magna Graecia and Sicily, but there were probably others as well.

Typically, they would take the bones/fossils as evidence of the myths that the culture already believed, such as battles with Giants/Titans. It's really not much different that working other natural phenomena into their preexisting belief system, such as earthquakes in Sicily being thought to be caused by the movement of Typhon under the earth.

Source: "Travelling Heroes in the Epic Age of Homer" by Robin Lane Fox

I don't have anything regarding a T-rex, but I am aware that Xenophanes of Kos found fossil seashells in mountainous regions and deduced that the area in question must have, at one point, been underwater. Unfortunately, I can't give much perspective on this beyond noting how impressed I always am with the almost scientific reasoning of the learned Greeks of ancient times; I'd be really interested if anyone had a more thorough source on this topic.

Source: Concise History of Science and Invention