I think Aktung has the right of it: the dragon would need to quickly get a bite of a soft underpart... then retreat and let the poison work
There'd be no mileage in a close up brawl... I just don't think these two animals would know how to fight one another... chalk and cheese... although once the croc got a hold then it would just spin and tear, maybe even get a hold of the throat and suffocate it
My money's on the croc
__________________
|