If you want to tame a Spino, use a typical 4x4 trap, and if possible, lure it with a Pteranodon or Argentavis and put it in the trap. You can probably use a tranquilizer arrow, but tranquilizer bullets are more effective. Once you put it to sleep, put meat, marbled meat, fish meat, otoro, and kibble in your inventory. You can also get food locally. The unlock level for the saddle is 71.