Stethacanthus (the Ironing-Board Shark) is a primitive shark and lived in the Late Devonian Period. At around 2-2.5 metres long, it was a large shark for its time, though later sharks would dwarf this by far. Even so, it would have been a tenacious predator, whilst being relatively primitive compared to later sharks, it would have been a highly advanced shark at the time posing a threat to the far more primitive forms still abundant at the time. However advanced this shark was though, the large Arthodire Placoderm apex predators, such as the largest of them all Dunkleosteus, would have regularly attacked and devoured sharks like Stethacanthus. They were minor predators, in a world dominated in the seas by the Placoderms.