I ask a very detailed artist to draw what was described here once. He drew a picture of a Dinosaur.
The Leviathan he drew the picture of a winged almost dragon looking sea creature, a dinosaur of sorts only winged that breathed fire.
The leviathan has always interested me. Especially in light of that fact that the KJV uses the word "dragon" a few times. But, if we look at the leviathan in Job 41, we see:
v1, 2, 7 - It appears he is a sea creature, but one that is too mighty to be caught by rod and reel.
v3-6, 8-13 - He's obviously not a force to be trifled with.
v14 - He is not an animal that has been domesticated.
v15-17, 23 - He has scales. (Fish or reptile).
v18-21, 31-32 - Occam's razor says that he breaths fire. There are a host of different explanations, however. I say go with the simplest. He breathes fire.
v25-29 - After the breathing fire verses, its hard to not think of a western dragon when reading these verses.
v30 - He has sharp claws.
So, this one seems to be cut and dried as well, but I'll admit that I already have a preconceived idea of what it is, and it's hard to not read that preconception into the passage.
Here is a documentary that I found fascinating, and it explains how dragons could have breathed fire.
http://documentaryaddict.com/dragons+world+a+fantasy+made+real-12492-doc.html