The dragon is the hardest main boss to do so make sure to bring an army of pteranodons with at least 700 stamina, 1,000 mele damage and 10,000 health. Even if you want, maybe you can bring a quetzal so it can tank the damage while the pteranodon attack the dragon. Quetzal-passive-40,000 health (I know the dragon does a lot of damage)
The worst tips are "FeEd iT fORcETaMe" .... We get it, you're bad at the game. Downvote since I upset the whiners. Anyways, Therizinos works best if boosted properly and some decent saddles. Have Veggie cakes in their inventories and the more friends the merrier. If you have the ability, Magmasaurs are great as well!
You will see people here recommend a total of 20 dinos which is max, I don't, we all know ark's ark, and the boss glitches that comes with it.
I usually take 9-14 therizinosauruses or rexes (depending on how good saddles I've got, and riding on 1 yuty, making it a total of 10-15 dinos, it takes stress off the game, making it less likely that a glitch will occur, when starting don't mount til you're inside the battlefield, and stand still on the ground when timer hits 0.
All dinos should at minimum be lvl 150 wild perfect tamed dinos, if they got mutations, good, but not necessary, saddles are the most important thing.
Stats, I would say, 50-80k health, rest of points into melee, yuty should have 4k stam, 20k health, some weight sence you'll be riding it, rest into melee.
I had a nice little high level army of dinos but as i dodge one of his good ol, fire balls it killed every single dino in one hit. So there I am unleashing hell on it for killing my lvl 207 carno along with the others that wouldnt stand a chance. So yea I tried to avenge my army but died a gruesome death.
Use as many therizinos as you want since it does extra damage to carnivores technically since the therizino is an omnivore which means carnivore and herbivore put together so since the other half is herbivore it should block out that affect I would also recommend pumping damage and health. Thanks for using your time on my tip I hope it helps you beat the boss.