The largest known anthracosaur was Anthracosaurus, a predator. It could reach up to 12 feet in length.
Anthracosaurus is an extinct genus of embolomere, a close relative of reptiles that lived during the Late Carboniferous (around 310 million years ago) in what is now Scotland and England. It was a large, aquatic eel-like predator able to grow up to 3 m (10 ft) in length.It has a robust skull about 40 centimetres (1.3 ft) in length with large teeth in the jaws and on the roof of the mouth. Anthracosaurus probably inhabited swamps, rivers and lakes. Its name is Greek for "coal lizard".
Anthracosaurus is believed to have been a member of the Embolomeri, a sub group of the reptilomorphs. So far only elements of the skull are known, but if Anthracosaurus had a body similar in form to it relatives like Archeria, then the body and tail would have been long and slender and up to about three meters long. Long, slender bodies that are termed eel-like are commonly seen in carboniferous vertebrates since they allowed for easier navigation through clogged carboniferous swamps and water systems. Aside from some amphibians and reptilomorphs, xenacanthid sharks also display elongated eel-like body forms.
Anthracosaurus had long sharp teeth in its jaws, and also a second set on the roof of its mouth. These would have been used to spear and trap soft bodied prey such as fish and even other amphibians, which then would probably be swallowed whole.
Eogyrinus commonly reached 4.6 metres (15 ft), however, it was more lightly built.
Eogyrinus attheyi (from Greek eos, meaning "dawn", and gyrinos, meaning "tadpole") was one of the largest Carboniferoustetrapods, and perhaps one of the largest of its family, Eogyrinidae, at 4.6 metres (15 ft) in length.
Eogyrinus appears to have been a powerful swimmer that moved quickly through the water by swishing its long tail from side to side. It may have been a predator, lying in wait for prey in much the same way as a modern crocodile. It was a lightly built animal, weighing around 560 kilograms (1,230 lb). Although probably better at hunting in the water, Eogyrinus could probably have also made a grab for prey passing close by on land.
Fossils of Eogyrinus are known from northern England.
Recent studies by Jennifer A. Clack suggest that the amphibianPholiderpeton described by Thomas Henry Huxley in 1869 is the same animal as Eogyrinus. If this is so, then Pholiderpeton's name takes priority.
For the Carboniferous period Eogyrinus was a particularly large predator that had an almost eel-like body that measured out over four meters in length. This body, which featured limbs severely reduced in physical size, was an adaptation to swimming and hunting in Carboniferous swamps which would have been clogged with dense weeds, submerged plants and roots. A body with a very small frontal profile like Eogyrinus had would have had little difficultly in navigating the submerged obstacles, meaning that Eogyrinus could root out hidden prey no matter where they tried to hide.
In more modern times, Eogyrinus has been speculated to be synonymous with the genus Pholiderpeton. If this is correct then fossils attributed to Eogyrinus will have to be renamed and moved to Pholiderpeton since Pholiderpeton was named long before Eogyrinus was.