These creatures have quetzal kibble as their preferred kibble, which is extremely expensive, especially when you consider how useless these things are. However, it is beneficial to have a few of them if you are a fan of breeding, as their kibble is on the list of possible demanded kibbles for imprinting. Without using quetzal kibble, these creatures are a very long rough tame. I would recommend finding the lowest level male and female you possibly can, and bite the bullet and tame them with quetz kibble. If you find 2 of them with levels that are nice and low, it'll run you 10-15 quetz kibble. Then, if you want more females, I would suggest mating the 2 that you tamed a few times. Maybe collect 3-4 eggs and hatch them all at once. They are relatively short, easy breeds, and I would much rather spend a couple days breeding a few dimetrodons than spending all that quetz kibble.
Easy way to tame (Works if you have Argentavis or Quetzal):
Step 1: Go to the swamp with your Argentavis or Quetzal and search the area for Dimetrodon. Once one is found, pick it up and carry it somewhere safe (recommended: The Dead Volcano, or your base. Just make sure everyone is set to passive).
Step 2: Let it wander around for a while. Knock it out every so often to check on its hunger. If it is not hungry upon knockout, let it wake up and heal for a while. Repeat until it is completely starving.
Step 3: Once one of your checkups on the Dimetrodon via knockout reveals that it is completely starving, grab whatever meat you have as fast as you can (prime meat if its a high level). The starving status causes the Dimetrodon, as well as all other creatures tamed via knockout, to constantly eat every second until they are either tamed or not hungry anymore.
I did all of this myself at the Dead Volcano, which it arrived there via my male Quetzal, Flappy. Argentavis can also pick them up for delivery. Hopefully this helps.