

To make Mosasaur Saddle, combine Hide, Fiber, Cementing Paste, Silica Pearls, and Metal Ingot in a Smithy for 10 seconds. The Mosasaur Saddle unlocks at level 78 and requires 60 Engram Points.
Do the cave of the strong and immune at level 71.70 and 69
To unlock the mosa saddle with an arthro (strong cave first)
You can tame mosasaurs in a underwater cave at the right side at the top
There the stronger and slower dino in water