Dunkleosteus

Dunkleosteus ("Dunkle's bone") was a placoderm fish of the Late Devonian.

Description
Dunkleosteus measured 10 meters long and weighed 4 tons. Like other placoderms, they were heavily armored, and only the large skull plates are preserved as fossils. Dunkleosteus had no teeth, but rather sharp extensions of the jaws. These plates could bite at a pressure of 8,000 pounds per square inch, the second most powerful bite of any fish to have existed. This pressure puts the bite force of Dunkleosteus in the same league as that of predators such as Tyrannosaurus.

Classification and Discovery
Dunkleosteus was originally described as Dinichthys terrelli in 1873. However, the two species were separated in 1956, and the new name honored David Dunkle, who was then a paleontology curator of the Cleveland Museum of Natural History. Even today most specimens of Dunkleosteus still reside in this museum.

Dunkleosteus was part of the placoderm group, among the first jawed fish to exist. There are three (possibly four) species of Dunkleosteus known to exist so far.

Diet
Dunkleosteus was a carnivore, feeding on other placoderms and crushing through their armor. Fossil evidence suggests that they cannibalized each other when the opportunity presented itself, and that any armor was regurgitated instead of being digested.

It is believed that Dunkleosteus underwent a change of diet as it aged. Jaw morphologies suggest that a juvenile's jaws were stiff and it fed on soft-bodied organisms. The jaws of adults were better able to hold and crush through harder prey.

Dunkleosteus could open its mouth in about 1/50th of a second. The resulting suction would have pulled prey directly into its mouth. This is a technique still used by species of fish today.