Parts of animals are generally treated like whole ones, live or dead, under the law. You can't transport a python skin across an international border without a CITES permit, same as for a live python. You could sell it legally, though.
Native turtle shells, etc. theoretically can't be possessed in Ontario without a permit, except via one of several avenues such as the single specimen exemption, a legally hunted snapper shell, etc. Realistically, I doubt anyone would be coming after you for possessing something of this nature, though they'd probably be pretty upset if people were selling them. $$$ would create an incentive to come up with more such specimens, perhaps to the detriment of a population.