Question: Taking several notable real life inspirations from the animal kingdom I like to design a realistic Dragon towering any creature ever lived but has a nasty habit of generating sonic boom every where in its wake. What are the prerequisites my Dragon have to evolve in order to attain supersonic flight? 

I think it's must have close to a mammal blood circulation to supply ample oxygen to its already effective muscular system and is warm blooded like a cheetahs to give it energy for sudden rush of adrenaline, a crocodiles eyelids to cover it eyes, and so on. My concern is that this colossal winged breast would be too heavy and its skeletal structure have to be augmented naturally through evolution but I have no clues how any animal can survive unhurt after performing such a earth shattering feat any ideas? No tech pls and absolutely no thunderpants!

Answer: 
**Dragons would need to have a reason to be supersonic in order to evolve to do so.**

Being able to fly at supersonic speeds will have incredibly high metabolic and structural costs for the dragon. In order for one to evolve these traits, we need to answer the following question: why do supersonic dragons produce more offspring than non-supersonic dragons?

If supersonic flight doesn't get more food, or more mates, dragons won't evolve it. Similar non-supersonic dragons would outcompete the supersonic ones, since they would require far less food.

In nature, nothing else flies supersonic, and supersonic flight won't be worth its calories if its used to catch cattle or ponies or other such animals. That's not to say that it couldn't be useful, though. Dragons have projectile weapons, so if dragons mostly fight against other dragons, supersonic flight could give them a key edge in dogfighting, especially since the dragon they were closing in on wouldn't be able to hear them coming.

**Dragons would need to consume incredibly high caloric density food in order to evolve to be supersonic.**

It takes a *lot* of energy for an aircraft to reach supersonic speeds, probably more than an animal could obtain eating other animals. If dragons fly at supersonic speeds, they'll need to consume something more energetically dense. Something like oil.

If dragons consume oil from naturally occurring sources, they could directly burn this in an internal jet engine in order to achieve supersonic flight.

**The Ecology of Dragons**

Dragons are large creatures that eat oil. They both extract calories from it, and produce refined fuel which they burn in their engines. These engines resemble a pulse-jet engine, and are primarily comprised of carbon fibers and thermally resistant graphites which the dragons synthesize from their food.

Naturally occurring oil, of course, is rare, and as a result, dragons have become incredibly territorial. They've got large, stiff bodies covered in smooth scales to reduce their drag, and can launch flaming globs of tar at one another mid flight. Large dragons can fly at supersonic speeds, which gives them maneuvering advantages in their aerial fights over oil-rich territory. Because their bodies are stiffened for high speed flight, they can't turn their heads very much, so skill in dogfighting is key for dragons to protect their territories.

These supersonic dogfights, of course, are necessarily short, as the thick scales of graphite that dragons grow on the leading edges of their wings and along their heads slowly ablate during supersonic flight. Dragons prefer to cruise at fast subsonic speeds and use their size and breath weapons to dispatch smaller challengers if possible, rapidly accelerating into the supersonic regime only when absolutely necessary to outmaneuver an opponent. These graphite scales also provide a measure of resistance against the breath weapons of other dragons.

Larger dragons can grow these heat shields faster and thicker than smaller dragons. As this gives the largest of these creatures a major edge in combat, evolution has driven these majestic creatures to grow to truly colossal sizes.
Actually I think a smaller dragon would be more likely to achieve these high flight speeds. If for no other reason than it can help them escape larger dragons and can be used as a weapon. 

I don't think the dragon could reach these speeds by flapping their wings alone, especially since most dragons would already need magic just to fly because of their size. But if they are very fast and can fly high into the stratosphere, then turn down and dive, they might be able to break the sound barrier with just a little handwavium. This could have come about partly from escaping larger dragons, (fly higher than they can) and then attacking either prey or as another defense against the larger predators.

If it was used as an attack dive they might need reinforced heads and necks, but the sonic boom would really mess up another flying creature or any other creature it passes near.