Origins of Dragon stories
If
dragons are a conglomerate of actual creatures then it is likely they have
been invented from serpents or reptiles such as the large lizards we have
discovered in the world, smaller lizards and perhaps the cockatrice which seems
to be either a real creature that had the ability to spit paralyzing venom that
also had a negative effect on plants. You can kill any vegetation with a simple
solution of soap and vinegar with the soap offering adherence and the vinegar
drying out the plant and preventing photosynthesis. It is entirely likely that
a species of serpent or lizard lived with such venom.