Ok... Where do I start with Therizinosaurus... I'll start with location and taming. I play on ARK Mobile so this is a Therizinosaurus guide for ARK mobile.

Locate your Therizinosaurus

Therizinosaurus seems to wander in most places except the snow biome in the far north and the swamp. The Dossier is found in the swamp. I have found the creature roaming in many places, but you can usually find them the most near the green obelisk or on mountains. Once you have found a suitable Therizinosaurus, proceed.

Taming and KO

Therizinosaurus is a knockout tame. I would recommend crossbows or a dart gun. A tamed Tapejara could be super handy. Just make sure it is set to follow, or it will land. Once knocked out, if you have any soothing balm, use it. While you can buy soothing balm from the store, I think you should spend time to get the Artifact of the Hunter from the cave in the south, and tributing it to the green obelisk. This can give 10x soothing balm, bringing the taming rate from 0.875 to 8.75. If you do not have soothing balm, bring plenty of narcotics or biotoxin, and kibble. Therizinosaurus is a herbivore, and takes berries after taming.

Utility

Therizinosaurus is a good all around late game tame. It can drill through rexes with ease. It has a decent health pool, but it is not the fastest option and cannot carry too much. It has three attacks. Melee claw swipe, by pressing attack. This does knockback to enemies that are small enough. It also has a "Tickle" attack by swiping up, which does not do much damage, but can gather hundreds of fiber from bushes, thatch from trees, and get Plant Species X seeds and rare flowers in large quantities. Alt attack 2 is a bite, which does a good amount of damage, harvests hide from corpses, berries from bushes, and wood from trees.

Additionally, Therizinosaurus is a herbivore, and can heal very quickly from sweet vegetable cake. It has a 1 person saddle, and loves to ruin newbies. It is an aggressive creature with a high torpor drain. It is a bit larger than Baryonyx, and swims about as fast as it runs.

Overall rating

9/10, wish it was a bit faster but sacrifices must be made.

Hope this helped!