A (possible) biological explanation for LBT's Nightmare Dragon (or Wyvern)

Yeah LBT had a dragon in the TV show.

So, I saw a clip from a 1982 movie called The Flight of Dragons explaining how dragons can breathe fire and can fly. So what if applies to this dragon too which could explain why it has a big belly. The dragon has hydrogen in its belly, of which hydrogen is lighter than air and highly flammable. This hydrogen allows this dragon be able to chase Cera by flying sorta like a blimp. So, perhaps its bones and muscles have a honeycomb-like structure.