When killing one of these get a couple flying creatures that can really take a hit like a griffin or something. Also when trying to tame one of these you have to impregnate a Dino but before you impregnate a Dino you have to get the rhyniognatha to at least 100 HP then let it mate with a large dinosaur (I used a Rex) after force feeding the orb to the large dinosaur you get after killing a rhyniognatha. Then the rhyniognatha will leave you alone and you have to care for the impregnated Dino and give it all its cravings. After almost an hour your impregnated dinosaur will die unfortunately, and you have a juvenile rhyniognatha and then it’s like raising a regular baby Dino