Even earlier. There is mention of finding Giant’s bones in Homer’s Iliad.
There are certainly older references that sound like descriptions of dinosaur fossils, and certainly of later mammalian megafauna, but I think that 1600s is the oldest we can pin down specifically. In that case, though the bone is now gone, there was a drawing made at the time with sufficient detail to positively identify it as from a dinosaur, and even make a good guess at species.