Note: As any intrepid, digestive-tract-spelunking adventurer can tell you, the occasions upon which you'll find intact skeletal structures behind the maw of something large enough to swallow you whole are few and far between, and the skeletons you do find will likely be well on their way to dissolution. Other rarities include breathable atmosphere, and a liquid medium that isn't actively trying to dissolve you along with any of the skeletal structures you may have brought with you on the trip.
Those planning a belly-of-the-beast expedition would do well to ponder the last words of the legendary leviaphant hunter Ephrib Mairomuft: "Oh, this IS caustic. Wow. I should have slathered on a bit more oint--"