When: Late Devonian (380-360 million years ago)
What: Dunkleosteus is one of the biggest placoderms to ever swim in the paleozoic oceans. Placoderms were some of the first jawed vertebrates, and rapidly put these jaws to use, becoming the top predators of the devonian seas. Dunkleosteus was the apex predator of its days, with nothing to fear but other Dunkleosteus (some specimens show evidence of cannibalism). It reached lengths of up to 33 feet (~10 meters) and is estimated to have weighed 8,000 lbs (~3,600 kg). Studies have shown that these giant fish could open their mouths extremely fast, creating massive suction that would draw prey into their mouths. Larger prey would then be captured and crushed by the giant ‘teeth’ of Dunkleosteus. These animals did not have true teeth, but instead what served as their teeth were sharped and exposed projections of bone.
Placoderms were an early off shoot of jawed vertebrates, and have no living descendants. Modern fish are more closely related to land animals than they are to Dunkleosteus. This giant placoderm, along with the rest of it’s clade, went extinct at the end of the Devonian. Their disappearance is primarily attribute to large anoxic (a lack of oxygen) events on the ocean floor, which dramatically disrupted the food chain - leading to one of the largest extinction events in Earth’s history.