Yes, they did have knowledge of them, but used biblical explanations to explain a lot of it. For example, in the 1200's an Italian monk wrote, "For we have picked up and excavated near the top of a very high mountain, quantities of shells of those fishes which we call cockles or mussels, similar to those which painters use to hold their colors. And in that place they are found mixed with sand, and with round stones among them, both large and small, as if they came from rivers; and this is a sign that that mountain was made by the Deluge." The deluge meaning the great flood.

there was some knowledge before that. In England a megalasaurus thigh bone was unearthed i 1676, the chemist Robert Plott recognized that it could not be a current animal, so he thought it was from a giant man. They also found some teeth in England about 1700.

The Chinese had been finding bone since about third cent. AD and often attributed it to dragons.

So you have a choice of theories: great flood, giant creatures and/or dragons.