For the homecoming parade in October, the student advisory board for the University of Iowa’s 160-year-old Museum of Natural History (UIMNH) made a paper mache model of a nearly 400-million-year-old fish species. Held above the heads of two people by three wooden poles, the prop was about six feet long with a flat head and piercing round eyes, painted a dark gray.
“Shark!” some parade-watchers shouted. “Dunky!” cried the more enlightened.
Second only to Rusty the Giant Ground Sloth — another mid-’80s arrival to the museum — Dunky the Dunkleosteus is the most iconic exhibit inside Macbride Hall. The extinct sea dweller is likely one of Earth’s first apex predators, ruling the late Devonian Period (also dubbed the Age of Fishes).
The Dunk’s absolute tank of a skull produced one of the highest bite forces of any animal to ever live. Rather than teeth, it used the self-sharpening blades in its jaw bones to dispatch fish and even shelled creatures such as ammonites.
Paleontologists believe it could open its jaw within a fraction of a second, creating a vacuum to suck in prey like an underwater Kirby.
“He’s a really exciting version of a species that would have existed in the ocean that was here, and was at the top of the food chain,” said Jessica Smith, communications and engagement director at UIMNH. “Most of Iowa was a shallow tropical sea, so the sunlight could really reach down. There was a really diverse sea floor, and Dunky is definitely part of that story.”
Unlike modern fish, placoderms like Dunkleosteus only had bones in their head: a series of thick plates that, when assembled, form a skull that looks hauntingly similar to the face of the dead-eyed killer in life. Since the cartilage and tissues of its body couldn’t fossilize, scientists have only been able to estimate what the rest looked like. For generations, they’ve referenced other Devonian fish species with fossilized hind quarters, in particular the much smaller Coccosteus, for comparison. The largest and most popular Dunk species, Dunkleosteus terrelli, was thought to be between 13 and 30 feet long.
In a practical use of space — and also, perhaps, to sidestep the lack of consensus about length — the Dunky exhibit in Iowa Hall is a combination sculpture and mural, utilizing perspective to make the mildly terrifying 3D placoderm head emerging from the wall appear connected to several yards of body behind it, extending into a murky sea. The exhibit is also rich with smaller fish, crinoids, trilobites and other Devonian fauna you can find encased in limestone in Coralville’s Fossil Gorge.
On Feb. 21, 2023, Case Western Reserve University Ph.D. student Russell K. Engleman published a paper in the scientific journal Diversity called “A Devonian Fish Tale: A New Method of Body Length Estimation Suggests Much Smaller Sizes for Dunkleosteus terrelli.” In it, Engleman proposed a formula for determining the length of any fish from any era based on the orbit-opercular length, or the distance from the front of the eye socket to the back of the skull. Tested on thousands of species whose body length is known, Engleman’s equation is so consistently, meticulously accurate, it’s bound to become the standard.
This new formula halves common estimates for the Dunk, proposing the largest were 10 to 12 feet long. But still thicc. So thicc, it’s unlikely a paper mache effigy would be mistaken for a shark; more like a giant, scaleless, demonic goldfish. It’s a little like finding the skull of a pitbull and assuming it has the body of a mastiff. It’s still a bulky breed, just in a smaller package.
This relatively new discovery is unlikely to cause Dunkleosteous exhibits — which appear in almost all museums with Devonian galleries — to undergo emergency resculptings and repaintings. But at UIMNH, as elsewhere, it offers a fascinating new talking point for tours. And perhaps some inspiration for short kings everywhere.
“Something tells me that if Dunky were here today, he would be just fine with us overestimating his size,” Smith said. “He wouldn’t take it too personally.”
This article was originally published in Little Village’s December 2024 issue.