While Dimetrodon teutonis is the smallest species of it's genus, Tambacarnifex was average in size compared to it's closest relatives. Therefore this, otherwise small to medium sized, predator was suddenly among the largest carnivores of its ecosystem. However if we propose similar skull proportions for D. teutonis and Tambacarnifex as their next, better known, relatives, we end up with two quite different animals. For both species we only have fragments of the jaws but the dentition tells at lot. While in both cases the teeth are non-serrated and slightly curved, the Dimetrodon teeth are much more robust than those of Tambacarnifex, this might indicate niche partitioning. Tambacarnifex might have hunted smaller prey, maybe it even followed animals into their burrows, something impossible for Dimetrodon with it's long dorsal spines.
(in case you want the paper on this one let me know)