Diplocaulus is a genus of amphibians, lived in the Permian period ^{1), 2), 3)}, perhaps appeared from the Upper Carboniferous ⁵⁾. Diplocaulus salamadroides was first described by Cope in 1877 ²⁾ and very large species, D. magnicornis was also described by Cope in 1882 ³⁾. They lived in the non-marine environments, and would have been totally aquatic ⁶⁾.

Diplocaulus is a curius creature. They have a large and flat head, with posterior lateral horns, so their head looks like a boomerang. Their trunk are short and stumpy, their tails are flat and long (perhaps, reaching to a half of total body length ⁵⁾).

In some specimens, the width of skull is about 30 cm or more ⁶⁾, in this case, the body length will be nearly 1 m. But many specimens seem to range from several cm to 20 cm in skull width ⁶⁾.

There is a discussion that Diplocaulus were active midwater feeders preying on small animals using their unique physical properties of the head based on the experiments of the model in a wind-tunnel ⁴⁾.

But, their heads were too large, and their limbs were too small to walk on the land, and thus, they would have been bottom dwellars, or sluggish swimmers ^{5), 6)}.

Their eyes looked directly upward and their teeth are delicate and small ⁵⁾. Therefore, they meight have fed soft animals such as annelids in the mud, or may have been vegitable diets ⁵⁾. Anyway, they could not have been taking a active prey from the water ⁵⁾.

They may have blended into the mud or sand of bottom excluding their eyes, like some flounders species.

Diplocaulus might have made burrows in the mud to escape from predators, or may have burrowed to protect themselves in the dry season, namely, they would have been aestivators ^{6), 7)}. Actually, a cluster of juvenile Diplocaulus was found from the mud burrow, which had wounds bitten by Dimetrodon ⁷⁾ (which looks like a dinasaur, but is more related to mammals than to reptiles). Apparently, they had played an important role in the food web of predator Dimetrodon.