Dunkleosteus terrelli

Dunkleosteus was a Late Devonian armored placoderm, part of an early-diverging branch of jawed fishes. While Dunkleosteus bore no true, replaceable teeth as we see in sharks, ray-finned fish and tetrapods, they had self-sharpening, shearing bony jaw plates that would have still efficiently dispatched prey.

The proportions of Dunkleosteus have been a subject of debate recently. Once upon a time length estimates predicted sizes of up to 8 or more meters (25 feet), but with better information on how the head scales with the body, we now know Dunkleosteus was more compact, although at 5 meters (15 feet) you still wouldn’t want to share a swimming pool with one. Likewise, the fins and tail of Dunkleosteus once were commonly based on bottom-dwelling relatives; while that has shifted, exactly how equivalent Devonian ecosystems were to modern pelagic ones is still a matter of some debate.

Either way, the life appearance of Dunkleosteus has shifted significantly as more data became available over the last decade.