While the "IRL canon" you learn from unpaid-indoctrination-prison would have you believe these things were ttly reel, they logically could not have been. However, their concepts and designs are of very special interest.
Some seem to be based on dragons and other beasts from long, faded folklore. Others seem to be based on heavy machinery, like apatasaurs or craniosaurs. Or those parasarolophus, however you spell it, the trombone-head 'saurs.