Taming these things are confusing, but I believe I have figured out how they work.
Step 1 is to kill a wild rhynio (can be any gendrr) to get the pheromones, next it is best to make a trap, the best design i know of is basically a stone dino gate griffin trap, but with behemoth gates. Next you want to find a high level wild female rhynio. Think of the level of the rhynio as the taming effectiveness you will recieve 150 being max. Next you need to lower the rhynio to below 10% hp, you can net them to make this easier. Once it is below 10% hp you need a mount with a high drag weight in order to inherit the best stats, carch/giga have best chances. Feed the creature the phermone and mount it. The rhynio should impregnate it within a few seconds. DO NOT CRYOPOD THE DINO IT IMPREGNATED! YOU WILL LOOSE THE BABY! once your tame is impregregnated it will go through a gestation period and ask for cravings. It is important you furfill as many as possible as they have a major effect on the level the offspring will be and the stats inherited. Once the timer is complete your dino will fall unconscious and die, however you will now have a new perfect tame rhynio!
It’s just came out with the new update.To tame it is kinda like the reaper.But instead of u getting impregnated it’s ur Dino but use a disposable Dino as once it gives birth the creature dies.from my own experience you need to kill one then get its pheromone gland then feed it to I am pretty sure ur creature once u found one u want to tame then find one u want to tame then eat the gland then keep attacking it until it impregnates u then u have to wait for a bit and u need to feed ur dino random things cuz it craves stuff.What I got was black pearls Lazarus chowder and absorant.I think the more u feed it the more older the baby is once it bursts from ur dinos chest then u need to raise it from there
to get a high level it depends on the host dino, the best ones are gigas, carchas, and brontos at the top. and rhynios get stats based on the host. even being said, its not guaranteed the stats such as it might not get the 30 points into health that the host dino had to put it into a example, and another factor is you have to give the host cravings. if not it might not be a max level either, they also dont get the hosts speed stat, their cravins contains: carcha egg, quetz egg, giga egg, golden egg, all the rockwell recipes and i mean all, element, absorbent substrate, black pearls, and gasoline. if helpful punch the sky
The rhynio has a similar taming method to the reaper you have to kill a male to get a certain item then eat the item which is called fertile essence then you need to find a female rhynio and get is to under 10% of its health and will do a special attack to give you the baby but it has to be done in the air or underwater so it can use all of its legs as required unfortunately the female will only give a baby to someone that’s a higher or the same level as it although that’s not confirmed to stay in the game.