Diplocaulus are constantly picked on by swamp carnivores, even the sluggish Dilos, add on the fact that they are so painfully slow and it results in it constantly kicking the bucket.
For taming either take some strong tames to kill all swamp carnivores or, and this is worth noting, use a pteranodon/Tapejara to hook it out the swamp for easy pen taming
All these tips here tells you how to tame it... but what they fail to mention is the fact, you have to breed it on land, can’t move the egg and the baby HAVE to STAY IN THE WATER!! Don’t push the baby on land or it WILL EXPLODE!!!! I just watch my baby explode right before my eyes!!! Never have I seen a Dino exposed before!!!
They are skittish but not anywhere near faster than humans. They have low torpor and health, so tranq darts are recommended. Tamed like any carnivore, kibble is Archeopteryx. Can be found anywhere in and around the swamps.