Fun fact the Lystro is an ancient ancestor of mammals. When you see one tame it, they can be very rare. I suggest using mejoberries. These guys are tough, but can't take on fast dinos like Raptors. Trust me I learned the hard way... "Your Lystrosaurus lvl 13 was killed by lvl 23 Raptor".
Me and my tribe love our lystro. They honestly don’t have any use to us anymore as we have all maxed our levels. But these critters are certainly a nice form of company. To tame them you can take some mejo berries. I believe aquatic mushrooms may work too if you are on aberration.