Dunkleosteus was a large placoderm that lived in the late Devonian period, about 382–358 million years ago. It grew to 10 metres (33 feet), and was the top predator of its time and one of the top predators of the Paleozoic era.
Dunkelosteus belongs to the Placodermi, a large, paraphyletic clade of armour-plated fishes likely ancestral to all living gnathostomes. More precisely, it was an arthodire, part of a clade which possessed powerful, shearing jaws. Dunkleosteus remains have been found in late Devonian strata in Morocco, Belgium, Poland, and North America.
Three hundred fifty-eight million years ago, a shallow sea teeming with marine life covered Northeast Ohio. Dunkleosteus terrelli, the largest predator and one of the fiercest creatures alive in the Devonian “Age of Fishes,” ruled the subtropical waters. Up to 20 feet in length and weighing more than 1 ton, this arthrodire fish was capable of chopping prehistoric sharks into chum! Dunkleosteus had a massive skull made of thick, bony plates, and 2 sets of fang-like protrusions near the front of powerful, self-sharpening jawbones.
Dunkleosteus could concentrate a force of up to 7,400 N at the tip of its mouth, effectively placing Dunkleosteus in the league of Tyrannosaurus rex and modern crocodiles as having the most powerful known bite. Dunkleosteus could also open its mouth in one-fiftieth of a second, which would have caused a powerful suction that pulled the prey into its mouth, a food-capture technique reinvented by many of the most advanced teleost fishes today.
Due to its heavily armoured nature, Dunkleosteus was likely a relatively slow (albeit powerful) swimmer. By Devonian standards, Dunkleosteus was one of the most highly evolved animals. It was one of the earliest jawed fishes. Instead of actual teeth, Dunkleosteus possessed a set of long, bony blades that were extensions of its jaw that could slice through flesh and snap and crush bones and almost anything else. These plates also sharpened themselves every time the fish closed its mouth, in a fashion somewhat similar to rodent teeth.
Dunkleosteus terrelli was the largest and most well studied species, however, there were many other smaller species. Although many are based on sparse and fragmentary remains, there have been at least 8 accepted species. The following species are often considered valid: D. amblyodoratus, belgicus, denisoni, magnificus, missouriensis, newberryi, terrelli, and raveri.
Previous reconstructions were based on a placoderm that was much smaller, but had similar looking body plates. This placoderm is called Coccosteus. Unfortunately, Coccosteus lived in fresh water and thus had a very different mode of life, so it probably looked different. More recently, a reconstruction by Ferron et al. 2017 used inferences from Dunkleosteus pelagic swimming and feeding habits. They noted their lifestyle was similar to that of a pelagic shark and adjusted the body morphology to suit. This is also in agreement with Carr et al. 2010, that states the preserved fin outlines are more like chondrichthyans (sharks). Additionally, the size of D. terrelli is difficult to pinpoint. Inferences must be made about most of the body. As a result, maximum sizes have varied. Carr 2010 places a large D. terrelli at very conservative 4.6 m (15 feet), while Anderson and Westneat 2007 places a large one at 6m (19.6 feet).
In the most recent reconstruction attempts using jaw perimeter and pelagic sharks that had similar ecological niches, Ferron et al. 2017 places a very large specimen, CMNH 5936, at 8.79 m (28.8 feet). Although this estimate is large, Ferron et al. 2017 has a limit and says estimates of 10 meters are most likely overestimates.
Dunkleosteus lived during the Late Devonian time period, from 385 to 359 mya. When Dunkleosteus appeared, it quickly diversified into many species, however, it could not survive the end Devonian mass extinction events. Two extinction events occurred at the end of the Devonian, the Kellwasser Event and later the Hangeberg Event. The last event, the Hangenberg event, wiped out both marine and terrestrial vertebrates. It completely destroyed many marine ecosystems. By the end of the Devonian, 70 to 80% of all species on Earth, including all Placoderms were extinct.
Mouth & Jaws
Dunkleosteus may have had a skin covering its teeth making it resemble modern cetacean species; such as beluga whales. Dunkleosteus terrelli was one of the first true apex predators to appear on Earth (Anderson & Westneat 2007), meaning it could eat any animal it wanted and had very little predators. How could it do this? It's partly due to the animal's giant size and partly due to the jaws. Boney plates making up the jaws were sculpted into fangs and long slicing edges. The upper and lower jaws would also shear against one another causing them to self-sharpen!
Moreover, Anderson and Westneat (2007) studied the feeding mechanics and the bite force of Dunkleosteus terrelli jaws. They made two key findings. First, they discovered the jaws could rapidly open and close. So fast that Dunkleosteus could make a suction when opening, sucking prey into it. Secondly, they found the jaws to have a tremendous bite force, on par with giant crocodiles. One of the larger specimens studied, CMNH 5768, which is estimated to be 6 meters in length had a bite force of 4,400 N (989 pounds) on the cusps and 5,300 N (1,200 pounds) on the end of the blade. Putting this in terms of pressure, this is 147 million Pascals or 21,000 psi (Anderson and Westneat 2007).
Combined, Dunkleosteus could suck in and bite straight through any animal alive at that time, from the thick shelled Ammonites, to other Placoderms with body armor. In fact, a study by Hall et al., 2016 found scrape and puncture marks on other Dunkleosteus armor that were made by larger Dunkleosteus. This means they may have even eaten eat other!
Another interesting fact is the Jaw shape of Dunkleosteus changed as it grew from juvenile to adult. A study by Boyle et al. showed the jaw became more elongated and grew a longer anterior fang, or cusp. The study concludes as the animal grew, the diet shifted from soft-bodied prey, such as fish and sharks to larger armored prey, such as placoderms (Boyle at al 2016). This shift in diet is common in top predators as they grow from juvenile to adult.
In 1966, the Ohio Department of Transportation (ODOT) began construction on Interstate 71 in the shale-rich Big Creek Valley—a treasure trove of sediment and fossil material. Under the leadership of then-Director William Scheele, a team of Museum researchers led by Bill Hlavin worked in collaboration with ODOT to excavate an immense volume of fossil-bearing shale concretions from the construction site. A rich variety of fossil fish and plants from the Late Devonian were uncovered, and continue to be found in the Cleveland Shale today! The Museum has some of the world’s best-preserved Dunkleosteus terrelli fossils, including the giant armored skull on display in Kirtland Hall of Prehistoric Life, nicknamed “Dunk." Dunkleosteus terrelli is named for former Museum Curator of Vertebrate Paleontology Dr. David Dunkle and Jay Terrell, who discovered the first fossils of the “terrible fish” in 1867.
- In the Dinotopia books and movies a massive Dunkleosteus guards the underwater entrance to the subterranean caves that contain the strutters and sunstones.
- Dunkleosteus was the fifth most dangerous sea predator in Sea Monsters. The show counted down the top 7 most dangerous sea creatures in history. It was depicted as being cannibalistic and capable of bending metal.
- The Devonian predator also made a brief appearance in the video game ParaWorld.
- In the video game E.V.O.: Search for Eden, Dunkleosteus appeared as an enemy creature in the first time period, and the player could evolve its jaws and body, both being the strongest in those categories.
- China Miéville's novel The Scar features Dunkleosteus, where they are also referred to as "bonefish".
- In Ecco the Dolphin, Dunkleosteus appeared as an enemy in the prehistoric levels. Ironically the Dunkleosteus existed in the Devonian period and the prehistoric levels takes place 55 million years ago. They were already extinct during that time. Even its echolocation sprite resembles a shark.
- It appears in Ark: Survival Evolved.
- Zack & Wiki: Quest for Barbaros' Treasure features the Dunkleosteus which is called the "Fountain Guardian". The Dunkleosteus had to be fished out to complete a puzzle.
- Dunkleosteus is also featured in the novel Meg: Hell's Aquarium as the first resident of the Dubai aquarium.
- Dunkleosteus appears in the second episode of Animal Armageddon where its extreme hunger drove it to extinction.
- It appears in Jurassic Park Builder as the first creature in the Aquatic Park.
- Dunkleosteus appears in Jurassic World: The Game as a legendary cave creature in the aquatic park.
- A school of small Dunkleosteus appears in the 2004 film Megalodon where they escape to the surface after the ground they were trapped under collapsed. One of the fish got into the oil rig and attacks a person before getting its head cut off.
- Dunkleosteus also appears in Prehistoric Monsters Revealed where it is depicted having a dorsal fin.
- The shark like monster in Monster Shark is part Dunkleosteus and part octopus.
- Dunkleosteus makes a brief cameo chasing an ammonite in the anime film Age of the Great Dinosaurs.
- A Dunkleosteus makes a cameo in the documentary Sea Rex 3D Journey To A Prehistoric World.
- The Dunkleosteus appears as a skin for the Great White Shark in the game Depth.
- The Dunkleosteus appears in the popular television series River Monsters during the Prehistoric Terror episode.
- Dunkleosteus also appears as the second boss of the North Sea fishing area in the mobile fishing game Fishing Strike.
- Anderson, P.S.L.; Westneat, M. (2009). "A biomechanical model of feeding kinematics for Dunkleosteus terrelli (Arthrodira, Placodermi)" (PDF). Paleobiology. 35 (2): 251–269. doi:10.1666/08011.1. S2CID 86203770.