TIFFANY GUO
Guest Blogger
If you’ve ever followed up a trek along Highbank’s shale bluff by wandering around the nature center, you may have come across what looks like the mounted remnants of an ancient, monstrous sea creature in the otherwise quaint surroundings. This is the jawbone replica of Dunkleosteus terrelli, a bony fish dating back to The Devonian Period, around 400 million years ago. Nestled right in the middle of the Paleozoic Era before the time of dinosaurs, this period is known fondly as the “time of fishes” for its abundance of strange, rapidly-diversifying sea creatures. Ohio was then a shallow sea, a reservoir of ancestral fish that preceded those we know today. To this colossal predator which terrorized the oceans back in its day, the world must have looked like a tame playground.
In its time, Dunkleosteus terrelli was likely the largest and most undefeatable animal to have existed in Ohio. Despite lacking traditional teeth, Dunk had a ruthless bite. Its mouth could open in twenty milliseconds, creating a strong vacuum force that swept prey between its jaws. These jaws featured two razor sharp slabs of bony plate, one protruding from the top and the other from the bottom. Dunk could snap its jaws shut in as little as 60 milliseconds, ambushing and slicing its prey with enormous bite force almost too quickly for a human eye to register the motion. Each time it opened and shut its mouth, the jaws would scrape against each other, one blade automatically sharpening the other. The brutal combination of rapid efficiency in both opening and shutting the jaws, along with exceptional bite force, is typically unheard of. Most top predators are advantaged in one or the other, but not both to this extent. This is the criterion that crowns Dunkleosteus terrelli as one of the first true apex predators.
Contrary to a mouth built with such weaponry, its body entirely consisted of soft cartilage. Dunkleosteus was a placoderm, a group of fish confined entirely to the Devonian Period. Placoderms (its ancient Greek roots meaning “plate” and “skin”) had heads of bony plates and cartilaginous bodies, appearing in sizes from 10 centimeters to 10 meters long. Even in current scientific research, estimates of Dunk’s specific size usually fall between 10 and 30 feet.
What complicates size estimates further is that fossil records of placoderms are somewhat incomplete. This is partly because cartilage, which made up the bulk of a placoderm, is a delicate material and doesn’t compare to bone in terms of durability. It’s often too fragile to fossilize, even in ideal conditions. Shrouded in mystery, Dunk’s body shape and size are still a topic of debate, with recent discoveries suggesting a shorter but chunkier build, more like a tuna than a shark. Fossils of Dunkleosteus tend to outline only its head with its plates of bony armor, the rest of its soft body lost to time and sediment.
The Devonian Period’s last years saw mass marine extinctions due to reasons still debated. Leading theories include plunging oxygen levels in the sea due to the explosion of algal blooms, which pull massive amounts of oxygen from the water as they decompose. Either way, Dunkleosteus terrelli’s grip on the planet loosened as the Devonian period fell victim to a changing planet, before newer marine predators would ascend the ranks to replace it. The extinction of Dunkleosteus is a testament that even an animal of such reigning terror is not immune to the elements. Our first apex predator was laid to rest by the water itself, sinking to the seafloor and immortalized by the mystique of its fossil remnants and the glory of its title.
Wow! Great history lesson!