Again appling that some how people like Christopher columbus and Marco Polo who wrote about such beats did not know what they were describing or talking about?
The Marco Polo passages could be describing a crocodile, Marco was not known to be the most objective observer. This is just a story and is not evidence at all. If they were dinosaurs he saw, why is there nothing in the Chinese record. Isn't it simpler that Marco screwed up a little or misinterpreted a story than the whole Chinese empire was in on the deception? This is your evidence?
As for Christopher Columbus please provide the relevant passages to back up these assertions.
Facts don't lie or have an agenda. Facts are just facts