Dunkleosteus is an extinct genus of arthrodire placoderm fish that existed during the Late Devonian period, about 358–382 million years ago. The name Dunkleosteus combines the Greek ὀστέον, osteon, meaning "bone", and Dunkle, in honor of David Dunkle of the Cleveland Museum of Natural History. It consists of ten species: D. terrelli, D. belgicus, D. denisoni, D. marsaisi, D. magnificus, D. missouriensis, D. newberryi, D. amblyodoratus, and D. raveri; some of which are among the largest placoderms to have ever lived. The largest species, D. terrelli grew up to 8.79 m (28.8 ft) long and 4 t (4.4 short tons) in weight. Dunkleosteus could quickly open and close its jaw, like modern day suction feeders , and had a bite force of 6,000 N (612 kg f ; 1,349 lb f ) at the tip and 7,400 N (755 kg f ; 1,664 lb f) at the blade edge. Numerous fossils of the various species have been found in North America, Poland, Belgium, and Morocco.
Dunkleosteus was named in 1956 to honour David Dunkle , then curator of vertebrate paleontology at the Cleveland Museum of Natural History. The type species D. terrelli was originally described in 1873 as a species of Dinichthys. Dunkleosteus is an arthrodire originally placed in the family Dinichthyidae, which is composed mostly of large, carnivorous fish like Gorgonichthys. Anderson (2009) suggests, because of its primitive jaw structure, Dunkleosteus should be placed outside the family Dinichthyidae, perhaps close to the base of the clade Pachyosteomorpha, near Eastmanosteus. Carr and Hlavin (2010) resurrect Dunkleosteidae and place Dunkleosteus, Eastmanosteus , and a few other genera from Dinichthyidae within it. Dinichthyidae, in turn, is made into a monospecific family.