It's a dragon, but its description vividly paints it as looking something other than a dragon. It is the offspring of Leviathan after all.
The earliest Life of St Martha was written in Latin at some time between 1187 and 1212. One episode tells how, soon after coming to Tarascon, she heard that people there were terrorised by 'a huge dragon, part land animal and part fish' which lived in a forest beside the Rhône and had killed many people passing the spot or crossing the river. Attempts to destroy it always failed, since it would hide underwater. The description of the monster is vivid and detailed, and by no means that of a conventional dragon:
It was fatter than an ox, longer than a horse, with a lion's face and head, teeth as sharp as swords, a horse's mane, its back as sharp as an axe, bristling and piercing scales, six feet with bear's claws, a serpent's tail, and a shell on either side like a tortoise.
- - -
She found the dragon in the forest, eating a man it had throttled. She threw over it some Holy Water which she had brought and showed it a wooden cross, and the defeated dragon stood as quiet as a lamb. The saint bound it with her girdle, and the people slaughtered it at once with spears and stones.
That said, George is sure of himself that he's stronger than Jeanne.