Dunkleosteus: The Rise and Mysterious Fall of the Prehistoric King of Cleveland

2015-04-01T09:12:30+00:00 March 31st, 2015|

By Matt Stansberry, Illustrations by David Wilson

“An unavoidable corollary of natural selection is that Nature never repeats itself. Indeed, Nature cannot repeat itself. Some may find this unsettling but, given the near total change that this place has witnessed, and will again, equally as many should find in it comfort, and a new respect and humility.”

– John Riley, The Once and Future Great Lakes Country

It lurked in a dark corner of the Cleveland Metroparks’ Rocky River Nature Center, past the taxidermy turkeys and the fish tanks full of pedestrian minnows.

I had brought my boys to the Nature Center to learn about how an acorn sprouts, to examine a rat snake’s shed skin. We watched a tufted titmouse at the birdfeeders, and took in the modest fauna of the Upper Midwest.

We had no idea that one of nature’s most flagrantly bestial experiments lay in wait.

[blocktext align=”right”]It looked like an orca whale hybridized with a demon beaver from hell, a buck-toothed killing machine.[/blocktext]I turned a corner and came face-to-face with a fiberglass monster. It looked like an orca whale hybridized with a demon beaver from hell, a buck-toothed killing machine.

The twenty-foot replica of Dunkleosteus took up an entire wall of the nature center. This giant armored fish swam in the shallow seas covering Cleveland 365 million years ago, during the Devonian Period or “The Age of Fishes.”

My sons stuck their heads inside of the beast’s open mouth, as hundreds of other kids had done before, rubbing the paint off of the Dunk’s massive bony jaws.

This megapredator seemed so incongruous, surrounded by the small, brownish denizens of the eastern forest. And yet, the bones of this fish had fallen out of a cliff wall just a couple hundred yards away.

Staring at the giant replica of the Dunkleosteus, I had to reconsider my preconceived ideas about what it meant to belong, to be from a place. How could a landscape change so much?

I decided then to study this epic fish, reading books, visiting museums, and talking to scientists, to try to get my head around Cleveland’s freakish fossil record.

***

Let’s try to unpack this statement: 365 million years ago Northeast Ohio was under seawater.

The 365 million number is incomprehensible and nearly meaningless.

“It’s hard to grasp the concept of 365 million years ago,” says Glenn Storrs, Curator of Vertebrate Paleontology at the Cincinnati Museum Center. “People try to put the geologic timescale into context using clocks and distances as analogies. The presence of humans in the history of the planet occurs in the last second of a 24-hour clock. These fish are 10 minutes to the hour.”

How are we supposed to process that massive span of eons? How do you propose to keep any appointments with the immensity of geologic time in the forefront of your mind?

[blocktext align=”left”]How could anything trivial matter when 365 million-year-old fish bones are falling out of the cliffs around Cleveland?[/blocktext]How could anything trivial matter when 365 million-year-old fish bones are falling out of the cliffs around Cleveland?

Since I have started studying the Devonian Period, I’ve stopped cutting my toenails. I left up the Christmas tree, and have refused to eat anything but chocolate-covered macaroons until someone gives me a good reason that’s not obliterated by the span of geologic time.

But let’s not dwell on my descent into nihilism. Instead, let’s consider plate tectonics and global sea level fluctuation.

365 million years ago, Cleveland was jammed up against Morocco.

“Land masses ride on the continental plates,” Storrs says. “Continental movement can be measured today – we drift a few centimeters per year. The continents can move a long way in those vast amounts of time.”

The climate was warmer 365 million years ago. The polar ice caps melted, and a shallow “epi-continental” sea covered the low-lying areas of North America.

“Shallow seas have covered most of the world at some point in time,” Storrs says. “That was the case for Ohio for hundreds of millions of years. These shallow seas were only couple hundred feet deep, not like the deep oceans of the nid-Atlantic or mid-Pacific. To the best of our knowledge, the sea receded at about the end of the Devonian period.”

Devonian Cleveland sounded really nice – warm, shallow water, lots of sea life. I asked Storrs if it may have looked something like the Caribbean.

He said nope. Apparently it’s always been kind of a shithole.

The top of the water column was full of giant predators that could bite you in half, and underneath was a thick layer of black, stagnant ooze.

A portion of the North American continent was rising at that time and rivers were draining sediment into the sea, creating a muddy runoff. This mud layer had accumulated to produce a soft sea bottom, and when animals died their bodies sunk into the muck and were buried quickly.

In most marine environments, dead fish rot. Aerobic bacteria destroy cartilage and soft tissues, and currents disperse the skeleton.

But on the nearly lifeless sea floor around Cleveland, there were no scavengers or bacteria to feed on animals that died and drifted down to the bottom.

[blocktext align=”right”]“Organic material didn’t deteriorate in this anoxic environment,” Storrs says. “It’s great for preserving fossils.”[/blocktext]“Organic material didn’t deteriorate in this anoxic environment,” Storrs says. “It’s great for preserving fossils.”

That thick layer of ooze eventually formed what’s known as the Cleveland Shale, a flaky, black sedimentary stone that stretches across northern Ohio.

The fossils found in the Cleveland Shale, especially of the sharks from that time period, preserve an incredible level of detail, including body outlines, impressions of skin textures and soft tissues.

Devonian fish and sharks lived all over the planet’s oceans. But Cleveland happens to have the world’s best-preserved specimens due to the unique geology of the Cleveland Shale.

And no species garners more attention than the mighty Dunkleosteus terrelli.

***

Dunkleosteus embodies the spirit of Cleveland.

It’s almost as if you asked my thirteen-year-old self to make up a life form.

The greasy kid wearing skate shoes and a Metallica T-shirt thinks for a minute. “So it’s like a 20-foot-long fish, with huge teeth. No … not teeth, cleavers made of bone! It has this armored helmet. And it eats sharks!”

DunkFinalWebIt was the king of its environs, literally the most badass predator on the planet. A world champ you might say.

Ask any professional sports fan – there just aren’t that many opportunities for Cleveland to be the best at something. So of course this happened hundreds of millions of years before any of us were around. It’s like those ancient stories about the Browns winning four NFL world championships before the Super Bowl existed.

Of course, many of the earliest discoveries of Ohio’s Devonian fossils were shipped off to New York and London, before the Cleveland Museum of Natural History existed.

Adding insult to injury, in 1985, the Ohio state government made Isotelus Ohio’s official fossil. Isotelus is a trilobite that existed between 430 and 480 million years ago. It’s essentially a cross between a shrimp and a speed bump. Thanks a lot, Columbus.

While that prehistoric pill bug is the state fossil, Clevelanders celebrate Dunk with sculptures, Dunk mugs and T-shirts. It’s our T-Rex.

Count Bill Hlavin among the Dunk obsessed. For the last thirty years he’s run an Akron-based oil and gas consulting firm, plying the shale for fossil fuels rather than fossil fish. But half a lifetime ago, he was Associate Curator of Vertebrate Paleontology at the Cleveland Museum of Natural History.

Dunkleosteus was the largest living vertebrate in its time,” Hlavin said. “And there were lots of them. We know from the amount of remains we find in a small area, they were very prolific. You wouldn’t want to be on a boat in the Devonian sea. You’d be gone in a minute.”

Hlavin studied Devonian fish under the former museum curator David Dunkle, whom Dunkleosteus was named after in 1956, and left the institution on unpleasant terms. Cleveland Scene published a good piece on the grudge that’s lasted nearly a half century.

[blocktext align=”right”]”You wouldn’t want to be on a boat in the Devonian sea. You’d be gone in a minute.”[/blocktext]While Hlavin isn’t in the fossil fish business anymore, you wouldn’t know it by visiting his office, which is strewn with artwork featuring Devonian sea monsters.

“There are at least forty different species of fish found in the Cleveland shale, but naturally Dunkleosteus was the king,” Hlavin said. “Why so big? There are all kinds of theories as to why — favorable temperatures of the oceans, lots of oxygen in the water, a tremendous food supply.”

But it’s hard to stay on top. Eventually Dunkleosteus and the entire order of armored fish (Arthrodires) went extinct, while sharks survived.

“Maybe the Arthrodires became too top heavy with their armored heads. The sharks were sleeker and faster,” Hlavin said. “The sharks were incredibly smooth and simple, and they really haven’t changed much through time.”

Scientists are close to having a theory for the collapse of the armored fish at the end of the Devonian. “But I don’t want to speculate on what that might be,” Hlavin said.

Both Hlavin and Dr. Joseph Hannibal, curator of invertebrate paleontology at the Cleveland Museum of Natural History became visibly excited when I asked about the extinction of Devonian armored fish, but neither would offer a guess.

“What ended the Arthrodires? That is the big question,” Hannibal said. “There’s some kind of filter – the sharks made it, and the armored fish did not. There are clear theories for the extinction of the dinosaurs, but not for this. There are some interesting things going on, strange deformations in our rock layers. We’re trying to interpret those. But would I be willing to hazard a guess? No, because we’d be scooped, or worse, be horribly wrong!”

***

When you walk through the Kirtland Hall of Prehistoric Life at the Cleveland Museum of Natural History, your eye is drawn to the Cretaceous land giants, a towering Tyrannosaurus squaring off against a Triceratops. It’s easy to miss the grinning, charcoal-colored Dunk skull, lurking in a corner display.

Paleontologists estimate those terrible jaws had a bite force of 80,000 pounds per square inch, one of most powerful bites in the world. The fish could also open its mouth quickly, in just one-fiftieth of a second — which created a strong suction force, pulling prey into its mouth.

While the assembled skull is impressive to behold, it didn’t start out that way.

dunkfinalwebspotDeep in the bowels of the Cleveland Museum of Natural History, Hannibal had shown me an un-prepared Dunkleosteus specimen, the exposed black bones locked in a large split stone.

The bones had flattened over the eons, under pressure and layers of sediment. The pieces were scattered and overlapping, and looked more like broken dishes than the remains of a big apex predator.

It’s hard to comprehend how much these fossils are “made” or interpreted rather than found whole.

Museum technicians have to actually break the bones to make them curved and round again, and then glue them back together. In many cases, scientists are really just guessing what the animal looked like.

“It’s like putting together a plastic model kit that’s been melted down,” Hannibal said. “Fossils are flattened so you need to re-inflate them.”

In cases where bones or pieces are missing, preparators cast mirror images to create replacement parts. There are varying schools of thought on how much visual differentiation there should be between recreated parts and actual bone. For example, with the famous Lucy skeleton, the recreated bones are set off in a contrasting color. In the museum’s large Dunkleosteus skulls, the recreated portions are a similar color as the actual bones, but are easily delineated by texture.

“People reconstruct things so that they look complete, to give the impression of the whole thing without counterfeiting,” Hannibal said. “Most of our fossil collections are 75-80 percent real. We put up what we have, and fill in the missing pieces the best we can.”

[blocktext align=”left”]“After looking at all of those specimens, I can unequivocally say that the collections we have at the Cleveland Museum of Natural History are the finest collections in the world.”[/blocktext]And with Dunks, there are a lot of missing pieces. The skulls and armored pieces of the Dunks are really all that survived the last hundreds of millions of years of compression and erosion. The rear portions of the body were cartilaginous and dispersed.

So how did scientists decide what a Dunkleosteus looked like if all they have is a skull? For that, we need to go to Scotland, and a Devonian geological formation called the Old Red Sandstone.

“There was a man in England in the 1840s by the name of Hugh Miller,” Hlavin explains. “He worked in the quarries, splitting the flags and finding all kinds of fish from the Middle Devonian. One of those fish was named Coccosteus, little animals, maybe a foot or two long. It’s like a miniature Dunkleosteus. There are hundreds if not thousands of Coccosteus specimens with the body outline and shape preserved. That species provided the standard for reconstruction of the Dunkleosteus body and all other armored fish.”

When Hlavin was working on his doctoral dissertation, he looked at every specimen of Devonian armored fish found around the globe. “After looking at all of those specimens, I can unequivocally say that the collections we have at the Cleveland Museum of Natural History are the finest collections in the world.”

***

Not to get all metaphysical, but I write this nature column to feel better about our place in the universal order.

I want to connect with our landscape, to illustrate some larger shared experience. I don’t usually know where the columns are going to go when I start writing.

I would almost compare it to fishing, where I feed out a line, not knowing what’s going to bite. In this case, I let my bait sink deep and thought I’d snagged my line on the bottom. And then the bottom started to move, to swim away. I had to cut the line.

Writing about Dunkleosteus has forced me to confront anxieties too big to name.

[blocktext align=”right”]What kind of benevolent personal God would spend hundreds of millions of years tinkering with sea monsters doomed to extinction?[/blocktext]I can see why creationists want to believe the world is about 10,000 years old. What kind of benevolent personal God would spend hundreds of millions of years tinkering with sea monsters doomed to extinction?

The inventiveness and indifference of nature, the sprawling scope of geologic time, the repeating cycles of species diversification and mass extinctions – these ideas have rattled me to the point of incoherence.

In fact, I need to compartmentalize and ignore what I have learned about this animal in order to function.

There is a term from psychology called negative capability – the capacity to hold conflicting concepts in the mind at the same time. Intellectually I know Dunkleosteus exists, but I ignore its existence in order to continue puttering around on Twitter, to perform my daily tasks.

There was a moment in Joseph Hannibal’s office at the Cleveland Museum of Natural History, where I looked up at where he sat, surrounded by bookshelves draped with four-foot-long rubber millipedes.

I asked him what the long-term study of ancient prehistory might do to a person’s mind.

He didn’t really look up, but muttered a rambling response on some other topic altogether.

The museum’s public relations person looked at me worried, and asked, “Did he answer your question?”

Yes.

Matt Stansberry was born in Akron, Ohio. He is a dad, nature writer, and fly fisherman. Find him on Twitter @LakeErieFlyFsh. More of David Wilson’s illustration work can be found at dwillustration.com.

Matt and David’s monthly column, “North Coast Biodiversity,” is collected here. Preorder copies of the first edition of Redhorse — a print collection of the first six “North Coast Biodiversity” columns — here, and signed prints of David Wilson’s original art for the column here

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2 Comments

  1. Mark R. March 31, 2015 at 11:55 am - Reply

    Good call, man. This stuff is frightening and does stuff to the brain – but maybe that’s good?!! I love these discussions – check out our site, we talk about this stuff a lot.

  2. Natasha Wilcox March 31, 2015 at 12:39 pm - Reply

    Deep in the bowels of the Cleveland Museum of Natural History, its new for me. Thank you for sharing us

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