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

More Diplocaulus Taming & KO Tips