Dunk Was Chunky, but Still Deadly

With a chew that might cut up a shark in two and an armored mug solely a mom might love, Dunkleosteus was certainly one of Earth’s earliest apex predators, terrorizing subtropical seas 360 million years in the past in the course of the Devonian interval. By some estimates, the monster fish measured so long as a college bus.

Nonetheless, a brand new research is taking a large chew out of Dunkleosteus’s estimated dimension. Russell Engelman, a paleontologist pursuing his Ph.D. at Case Western Reserve College, lately in contrast the proportions of Dunkleosteus’s armor-clad head to the cranium sizes of a whole lot of residing and fossil fish. Final month, within the journal Variety, Mr. Engelman concluded that these historic fish maxed out at solely 13 toes and had been formed extra like stocky tuna than svelte sharks.

For the research, Mr. Engelman examined a number of Dunkleosteus terrelli specimens on the Cleveland Museum of Pure Historical past. Many of those fossils had been found close by in cliffs alongside the Ohio River, making specimens of the “Dunk” a prehistoric icon within the metropolis. However little analysis had been carried out on Dunkleosteus’s dimension, and a number of the previous measurements appeared fishy to Mr. Engelman.

Dunkleosteus belonged to an historic faction of fish referred to as the arthrodires that dominated the seas in the course of the Devonian. As a result of the majority of Dunkleosteus’s physique was almost certainly composed of fragile cartilage, solely the thick armor plates that encased its head and neck had been preserved as fossils. Whereas these plates protect the predator’s jagged jaws, they reveal little about the remainder of its physique. In consequence, most efforts to dimension Dunkleosteus relied on extrapolating from the proportions of its a lot smaller kinfolk.

In accordance with Mr. Engelman, head size is a dependable proxy for physique dimension in fish: Brief fish species usually have shorter heads, and lengthy fish species longer heads. He targeted on the area between a fish’s eye and the again of its head. “The organism can’t mess with the dimensions of this space an excessive amount of as a result of that’s the place the mind and the gills are,” Mr. Engelman stated. “In case your gills get too small, you suffocate.”

He in contrast the dimensions of this area in Dunkleosteus to the pinnacle proportions of practically 1,000 different species of fossil and fashionable fish, ranging in dimension from smallmouth bass to giant sharks. After working the measurements by a number of fashions, he concluded that the common Dunkleosteus head, which measured round 24 inches, correlated to a fish barely longer than 11 toes. The most important identified Dunkleosteus topped out at round 13.5 toes. As a substitute of bus-size behemoths, these fish had been nearer to Volkswagen Beetles, however nonetheless bugs that might ship bone-crushing bites.

Lowering Dunkleosteus’s size additionally alters its proportions. Most reconstructions depict Dunkleosteus with the elongated physique of a shark. Nonetheless, extra full arthrodire fossils reveal that these fish had squatter, cylindrical our bodies. Mr. Engelman thinks Dunkleosteus in all probability resembled a rotund tuna.

This full-figured fish was like an armored Pac-Man. It had a mouth twice as giant as a fantastic white’s and possibly outweighed longer sharks. “Individuals say it’s pudge, however that’s in all probability simply stable muscle,” Mr. Engelman stated.

Because the paper’s publication, a number of individuals have referred to as the fossil fish “Chunkleosteus” on social media. However Mr. Engelman doesn’t assume the brand new estimates take something away from the traditional predator’s prowess.

“Individuals assume this can be a downgrade, however that is really an improve,” he stated.

Removed from a slow-swimming backside dweller, Dunkleosteus seems to have been constructed for quick actions in open water. And even a shorter Dunkleosteus was nonetheless the undisputed king of Devonian seas.

Not everybody is completely satisfied Dunkleosteus rocked a dad bod. Caitlin Colleary, a paleontologist on the Cleveland Museum of Pure Historical past, stated it’s powerful to inform for certain what Dunkleosteus actually seemed like with out extra of its physique. Whereas cartilage isn’t fossilized, the Cleveland Shale has yielded the cartilaginous our bodies of sharks that lived alongside Dunkleosteus.

“Don’t get me mistaken, I really like a chunky ‘Dunk,’” stated Dr. Colleary, who was not concerned within the new research. “However I’m not going to get too connected as a result of in science, particularly paleontology, it simply takes one new discovery to vary all the pieces.”