The debate was simple: did such a thing as a Dragon Cow exist? According to Thurston it does, and what separates it from the rest of the herd, is its ability to breath fire.
Sorry Dino, my love, but my money is on this spicy meatball.
Thurston: "It's a Dragon COW!"
Joseph: "There is no such thing! What is a Dragon Cow?!"
Thurston: "It's a Cow that breaths Fire!!"