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.