I wonder if its still inside the game somehow though, that would be interesting!
I sincerely doubt it. Iguana Entertainment had to do a ton of data compressing just to fit what we ended up getting onto the cartridge; there'd be no room left for extras. According to a Dienstbier interview, they were just an extra 50KB away from having a
Brachiosaurus in the Treetop Village, and as sad as he was about that getting cut, you can bet there wouldn't be unused models taking up space that could be used for it.

(and at any rate,
Kaiser once said that there wasn't much of anything else left in)