Dunkleosteus terrelli

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 6 m (19.7 ft) long and 1 t (1.1 short tons) in weight. Few other placoderms rivaled Dunkleosteus in size. Dunkleosteus could quickly open and close its jaw, like modern day suction feeders, and had a bite force of 6,000 N (612 kgf; 1,349 lbf) at the tip and 7,400 N (755 kgf; 1,664 lbf) 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.
Species
At least 10 different species of Dunkleosteus have been described so far.
The type species, D. terrelli, is the largest, best-known species of the genus. It has a rounded snout. D. terrelli's fossil remains are found in Upper Frasnian to Upper Famennian Late Devonian strata of the United States (Huron and Cleveland Shale of Ohio, the Conneaut of Pennsylvania, Chattanooga Shale of Tennessee, Lost Burro Formation, California, and possibly Ives breccia of Texas ) and Europe.
D. belgicus (?) is known from fragments described from the Famennian of Belgium. The median dorsal plate is characteristic of the genus, but, a plate that was described as a suborbital is apparently an anteriolateral plate.
D. denisoni is known from a small median dorsal plate, typical in appearance for Dunkleosteus, but much smaller than normal.
D. marsaisi refers to the Dunkleosteus fossils from the Lower Famennian Late Devonian strata of the Atlas Mountains

Four hundred million years ago, long before the dinosaurs walked the Earth, Dunkleosteus was at the top of the world's food chain. One of the first jawed animals on the planet, this prehistoric armored fish attacked its prey with bone-crunching ferocity.

> **Muscle Man:** This fish's body was bulky and extremely muscular. It needed the muscle power to propel itself through the water when it attacked prey.
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> **Bone Head:** Dunkleosteus' skull was made of several pieces of thick bone, giving it an armored plating that no other creature could break through.
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== Creature Features ==

### Size

Length up to 20 ft.; Weight up to 2,200 lbs.

### Where?

Fossils have been found in the eastern U.S., Germany, and northwestern Africa.

## Did You Know?

Dunkleosteus swam alongside the coelacanth, a species of fish that has survived into modern times.

* Millions of years after its death, the fossilized skeleton of Dunkleosteus is still a scary sight.

## B.T. (Before Teeth)

Dunkleosteus didn't really have "teeth," but jagged extensions of its jawbone. A first step in the evolution of teeth, the bones continually grew and stayed sharp as the fish used them to bite through prey. Thick and fang-like in the front, they could easily chop a large victim in half. In back the "teeth" were wide and a little smoother, like molars, and used for grinding food.

> **Protective Eyewear:** To keep them safe, Dunkleosteus' eyes were set inside four pieces of thick bone that formed a circular shield.
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> **Widemouth:** Each jawbone was connected to the skull by a set of hinges, allowing Dunkleosteus to swing open both the upper and lower jaws in a huge gape.
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== It's a Snap ==

1. Seeing a primitive ray-like fish swimming nearby, dunkleosteus turns its massive body around in pursuit of the meal.

2. Closing its sharp jawbones together, it not only rips a chunk out of the victim's body, but severs it in half for an instant kill.

Dunkleosteus was one of the most powerful fish in the Devonian seas. Instead of teeth, this predator had blades of solid bone that could slice and crush just about any creature it found.