A Mid-Permian Pelycosaur Predator — Dimetrodon limbatus — above
The famous fin-backed pelycosaur, Dimetrodon ( 'two-types of teeth' - 3m long ) needs little introduction. Despite its sprawling stance and thick-limbs, the toothy
Dimetrodon and its kin were the top, unrivalled land predators of their time.
So, what did pelycosaurs use that big fin for? Some say temperature control. If so, it is very odd that only some pelycosaurs were endowed with this dorsal radiator.
Perhaps it depended upon environment. Dimetrodon and Edaphosaurus, the sail- backed plant-eater, may have lived in open, sunny areas while their finless
equivalents, Sphenacodon and Casea, dwelt in heavily forested regions. Under the treed canopy, a large fin would offer no advantage in controlling body temperature and the
tall spines supporting the fin would make manouvring beneath low branches very awkward.