How to tame an ichthyosaurus:

1. They are passive tames, you don't knock them out to tame them.

2. I recommend taming an ichthyosaurus that is in shallow water.

3. After you find an ichthyosaurus, you will need to feed it meat or preferred kibbles. Also, raw meat works better than raw fish meat.

4. Keep feeding it until it's tamed.

-If you're on mobile and trying to complete the pursuit of taming an ichthyosaurus, you don't need to make a saddle. You will be given a saddle after completing this pursuit.

Hope this helped!

-Pablo27