Well, eastern dragons always reminded me more of a giant oarfish. And some central europe dragons weren't that far off, being described as flying snakes.

I think "every culture has a dragon" is kinda misleading.

"Every culture has a creature that got translated as a dragon" seems closer to the truth. The creatures themselves have a great variety between them.

Seems like many bones would do. Whales would be a lot more common i imagine.