Human players riding a dino player? Yup! The human player knocks the dino player out (make sure your hostile to them and have pvp ON so you're able to attack the other player) The human player needs to knock out the dino player. Just like you'd knock out a regular dino.

The human player then clicks on the dino player to "claim" you. This only works on dinos that need to be knocked out to tame them (as far as I know).

Then, you slap a saddle on the dino player (if possible) and a way you go! You both still have complete control over your characters, which is pretty cool! A powerful pairing in the right hands!

I hope I didn't forget anything lol. It's been a while.