Eogyrinus

Eogyrinus attheyi (from Greek eos, meaning "dawn", and gyrinos, meaning "tadpole") was one of the largest Carboniferous tetrapods, 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.