The mammoth already has a platform saddle in ark mobile but you have to buy the engram with real money. Click the up arrow if you want to help convince wildcard to add it into all versions of ark fully including ark mobile for free!!! Help start the petition revolution!!!!
This is way more versatile than the beaver and far easier to tame as well.
I've killed an alpha rex with mine, has a weight reduction on wood so it can gather an obscene amount in one trip, it has a really large AOE on its stomp which makes it amazing for collecting berries as well and it's the best early tame to clear out the Arctic as it's stomp cuts down wolf packs and annoying argies with ease.
Late game use it for its weight reduction alongside a beaver for collection if wood is a need to get both insane wood collection speed and large carrying capacity of wood
On mobile it can also wear hats so it can get insane armour from a good flak helmet making it unstoppable. Borderline as good as a rex once you spec into melee