380 million years ago there lived a giant, armoured fish that had a bite strong enough to puncture steel…
What was Dunkleosteus?
Dunkleosteus belonged to a group of ancient, armoured fish known as the placoderms. These fish lived during the Silurian and the Devonian periods - between 440 and 359 million years ago - and they were amongst the first fish to possess jaws.
- World's deadliest fish: you won't want to meet these fearsome species underwater
- Meet the most dangerous animals in the ocean
Before placoderms, jawless fish known as ostracoderms dominated Earth’s early oceans. Like placoderms, ostracoderms were also covered in bony plates, but devoid of jaws they were unable to bite prey in two like Dunkleosteus and other placoderms could.
How big was Dunkleosteus?
At roughly 4m in length, Dunkleosteus is the largest placoderm currently known to science. And this is just a recent, conservative estimate for this monstrous fish; some earlier, more speculative estimates placed its total length closer to 8m and similar in size to a large orca.
Dunkleosteus’skull alone is nearly 1m-long, which makes it not only one of the biggest fish of its time, the Late Devonian, but of all time. However, it’s not just Dunkleosteus’ size that has earned it the title of “prehistory’s most fearsome fish” - its jaws were also particularly menacing.
How strong was Dunkleosteus’ bite?
Dunkleosteus lacked proper teeth; instead it had two pairs of long, bony blades that protruded from its upper jaws and its lower jaws, creating a cutting apparatus that crudely resembled a guillotine. At the tip of these blades, or fangs as they’re commonly referred to, Dunkleosteus was capable of biting down at a force of 80,000 psi, which is a lot stronger than the bite force of an average lion and more comparable to the bite force of a large alligator and prehistory’s most infamous chomper - the T.rex.
- Which big cat has the strongest bite? And just how deadly is that bite?
- How powerful was the bite of a T.rex?
From close study of Dunkleosteus’ jaws, researchers have estimated that it was capable of opening its jaws in just 20 milliseconds, thanks to some specially designed joints working in tandem with several powerful muscles.
This is lightning fast; in fact, it’s fast enough to create a small vacuum just in front of Dunkleosteus’ mouth. It’s thought this vacuum effect may have helped Dunkleosteus ‘suck’ prey into its mouth before it bit down and straight through whatever its poor prey had to defend itself, whether that be a shell, bony plates, or just fleshy skin.
What did Dunkleosteus eat?
What Dunkleosteus ate is thought to have changed as it matured. The juveniles, whose jaws weren’t fully developed, fed on largely soft-bodied animals, while the adults dined on a variety of prey, from hard-shelled ammonites and small, armoured fish to other Dunkleosteus.
A specimen of Dunkleosteus actually shows damage consistent with bites from another Dunkleosteus - proof enough that this monstrous fish wasn’t above hunting others of its own kind. A specimen of Titanichthys, another giant placoderm thought to have rivalled Dunkleosteus in size, also shows signs of having been bitten by a Dunkleosteus.
Was Dunkleosteus a fast swimmer?
As well as having one of the most powerful bites of any animal ever, Dunkleosteus was also a fast swimmer. It was originally thought that, due to its relatively stocky build, Dunkleosteus was a bit of a slouch, but after the teeth of a fast-swimming shark known as Orodus were found in the stomach contents of a Dunkleosteus, there’s now evidence to suggest that it was fast enough to catch some of the fastest fish that it lived alongside.
Dunkleosteus, Titanichthys, and Orodus were all pelagic fish, meaning they lived primarily in the open ocean. Dunkleosteus is widely considered to be the world’s first pelagic super predator, occupying a niche that’s now ruled by great white sharks and orcas.
Why did Dunkleosteus become extinct?
Dunkleosteus faced extinction at the end of the Devonian, 359 million years ago. It wasn’t the only animal that disappeared at this time; as many as 70-80% of species became extinct at the end of the Devonian. However, what wiped out all of these animals is unclear and has left researchers puzzled for decades.
The leading hypotheses are that several global cooling episodes or a series of underwater volcanic eruptions triggered large-scale sea level changes and widespread ocean anoxia (i.e. a lack of oxygen available in water). There’s also been a suggestion that a comet impact may have triggered worldwide ecosystem collapse and that the Siljan Ring, a crater lake in Dalarna, central Sweden, may be the site of this supposed impact.
While the cause of this mass extinction may still be debated, it’s long been clear that many diverse groups of animals died out at the end of the Devonian. The placoderms, the group that includes Dunkleosteus and other giants such as Titanichthys, were completely wiped out, as were their jawless cousins the ostracoderms.
Interestingly, other jawed, non-armoured fish, such as the chondrichthyans (sharks) and osteichthyans (bony fish), were less strongly affected by this mass extinction. They diversified post-extinction, filled the niches left by the placoderms and the ostracoderms, and ultimately went on to establish the ecosystems we recognise in our oceans today.
- What was the first ever apex predator? Meet the prehistoric Anomalocaris who ruled before the dinosaurs
- Apex predators: All you need to know about nature's most ruthless hunters, including why they're vital to balancing ecosystems
- Deadliest apex predators in the wild: which ruthless mammals are the best killing machines?