We shouldn't be so ready to demand evidence when evidence is (at its foundation) arbitrary. It is evidence because it is observed. It is observed because it is sensed (via senses.) It is sensed via neurological dynamics. Neurological dynamics (brain activity) is very sensitive to changes because it is regulated by chemistry and electrodynamics. This is how there can exist illusions (situations in which one or more senses perceive something that is not) such as mirages. Therefore, all evidence requires some degree faith.
With that said, how do we know that all the creatures we think of as dinosaurs WERE NOT dragons, and that they never showed the wings at public excavations and exhibits?
Or, what if the process described by Agonaces of Susa is possible (fire-breathing?)
Methane at earth tropical temperature (around 29 - 35 degrees Celcius) has a specific heat, c, of 2.226 kJ/kg*K. If the heat of combustion of methane gas, H, is 55.5 MJ/kg, then the change in temperature, T, needed to produce a fireball is
T = H*c = (55.5 x 10^3 kj/kg)/(2.225 kJ/kg*K) = 24,943.8 K/kg = 24670.7 Celcius/kg.
This is the temperature change needed to explode one kilogram of methane, which is a ridiculous amount of gas. Humans pass 0.000026 kg of methane gas per incident, about 0.000359 kg a day of methane. You would need a temperature change of 0.65K to combust a fart, but the density of the gas in the anus is lower, and the velocity of the gas is so fast that this temperature change wouldn't be felt by the gases (the anus is around 37.5 C).
The tropical density of methane is 0.000717 kg/L, so if a dinosaur expels 15 liters of gas (~400x more gas than we expel), or 0.0717kg of methane, the dinosaur/dragon would only need a temperature change of 268K, or 23 degrees Farenheit. Heating gases can be readily achieved by holding the pressure constant and reducing the volume, or holding volume constant and raising the pressure. It is much more than plausible to believe dinosaurs had mechanisms to do this, however we have no "evidence" because no one even believes it is possible enough to research it. I am not saying this was a characteristic of dinosaurs/dragons necessarily, but it is definitely scientifically possible. And, it is scientifically probable also. Dinosaurs may have an organic adiabatic chamber to accomplish this.
There are excavation photos of people who have uncovered skeletal systems they think belong to the n'phiyl - humanoid skeletal systems between 9' and 35' tall. Yet, some people say these skeletons are fake. O.K., that is fine to entertain. But, if one entertains that this kind of historical find can be faked, why cant the findings of dinosaurs be a covered-up for dragons, or even completely faked?
So, before we say "show me the evidence" or "that is absurd," consider some of the stuff our matriarchs and patriarchs had to go through where they did not have the luxury of "modern science" to explain phenomena. If you were to bring a person from the dinosaur age to our time, very few people would take that person seriously. In 1000 years, the things we think are interesting but not mythical may yet become things of myths to those in the future. Does it mean it was a myth? Absolutely not.