Step 1: first you have to kill a male rhyniognatha and take the pheromone from its inventory

Step 2:take a Dino which can eat the pheromone I recommend taking a brontosaurus, rex ,yutyrannus and trike

Step3: find a low lvl female rhyniognatha (you can use high lvls also but they do more dmg)

Step 4: drop the female to below or 100 health (when you think you can 1 shot it use tranq arrows or a spear or pike) quickly feed ur Dino the pheromone before the rhyniognatha flees away

Step 5:your Dino will be impregnated and it will crave 5 different foods

(It's health will go down but don't try to heal it it's a waste of time and food) the time for the baby to come out will be 1 hour and feeding the 5 different foods is not compulsory but it will highly effect the lvl

Step 6: you now have a juvenile/baby rhyniognatha!!!!!