Just across from Donna the triceratops in Hillsdale’s Daniel M. Fisk Museum of Natural History lies a tiny tooth about three millimeters in length. It is a tooth that represents the glory days of Michigan’s history, when it was a shallow tropical sea poised mere miles from the equator and filled with an assortment of tropical fishes, sharks, brachiopods, corals, and reefs. It is a tooth that would have been found in the mouth of a two foot long shark that might have swum through campus over 400 million years ago.
When he found this small tooth in a publicly accessible fossil hunting site in Michigan, Professor of Biology Anthony Swinehart was able to identify its owner as Phoebodus sophiae, a shark that lived in the Devonian period between 419 and 368 million years ago. Swinehart’s specimen is only the third shark of this species discovered in North America, and only the third species of shark from the Devonian period ever found in Michigan. Swinehart is now working with the world’s foremost shark expert, Chuck Ciampaglio, to continue on-site research into the species and search for more specimens and possibly new species.
“The find was somewhat serendipitous,” Swinehart said, “but luck is where opportunity meets preparation.”
His story begins on a routine fossil hunt on August 23 in Northern Michigan. In addition to teaching biology courses at Hillsdale, Swinehart curates the campus museum, so he often spends his weekends combing through the silt and rock in search of fossils.
“I just want to get specimens for the museum,” Swinehart said, “but as I do that, I am an opportunist. If I see something that is unusual and hasn’t been fully explored yet, I will take that path, and that’s what this leads to.”
This particular trip, Swinehart was searching for “blue bits,” which are the color of fish material from Devonian rocks. The Devonian is known as the age of fishes. It was a time of significant radiation of different species of fishes and the origin of many lineages of fishes. Swinehart said this makes it important for understanding the evolution of the fishes and sharks both preceding and following the period.
“I was thinking of armor from armored fishes and I found some, but I was picking up every blue bit I saw,” Swinehart said. “And I saw a blue bit about the size of the head of a pin, and I thought, ‘Well, sometimes these are just the tip of the iceberg. So I collected all the blue bits and when I got this one out and looked at it under the microscope, it was a shark tooth.”
This tooth belonged to a species of shark never before discovered in Michigan, and one of only three Devonian species found in Michigan to date.
It was Phoebodus sophiae.
Besides opening up the species to new locations, Swinehart’s specimen is also the oldest of the species in all North America, and possibly the world, by 1.6 million years— and Swinehart found it in an already well-documented public dig site.
He explained that once a site has been thoroughly explored, scientists tend to move to “greener pastures,” where they have a better chance of finding exciting new specimens.
For Swinehart, though, combing through these sites only adds to the adventure and the challenge.
“There is always something more we can discover,” Swinehart said, “it just takes diligence. So, when I go fossil hunting, I am on my hands and knees. You can’t find new, unique things without really getting dirty and being thorough.”
The skeletal structure of Devonian period sharks renders them particularly difficult to find, Swinehart said. With cartilaginous spinal cords and skulls instead of bone, most of their skeleton—except their teeth and other small remains—breaks down instead of fossilizing. This contributes to the under-representation of known shark species from this period.
For some perspective, these teeth are so tiny that typically scientists discover them only by bathing whole swaths of rock in acetic or formic acid for several weeks until everything else dissolves and the teeth sink lazily to the bottom for easy observation and cataloguing.
But Swinehart, with his thick, coke-bottle glasses inches from the earth, found his tooth the old fashioned way. And he plans to find more.
“I mean, what are the chances that that is the only one in a hundred acre quarry,” Swinehart said. “There are probably more. They just went unnoticed. I guess it’s possible that it’s one of extremely few. We are going to find that out. We are doing more research, too.”
Matthew Hoenig ’17 studied under Swinehart while at Hillsdale. Though he didn’t enter Hillsdale dreaming to become a paleontologist, after a couple of dinosaur digs with Swinehart—during one of which he helped excavate Linda the triceratops—he said paleontology became his passion.
Working on digs with Swinehart was “very enjoyable,” Hoenig said. “I am glad to be able to continue to do so.”
Having just finished his master’s in earth & environmental science at Wright State University where his research involved cartilaginous fishes and sharks from Iowa and Illinois, Hoenig was a perfect candidate to help Swinehart continue his research.
“I helped him identify the tooth and also put it in paleontological context as far as the age of the rock and comparing that rock to the age of other localities from around the globe that have members of this genus,” Hoenig explained, helping to reveal the greater significance of this particular tooth.
Because of this, the tooth sets the species, and the entire genus, back as much as 1.6 million years, it also complicates the possible use of Phoebodus sophiae as a proxy index fossil. It was thought to be restricted to the Middle Givetian Age. The new find occurs within the Early Givetian. Index fossils are fossils of species that came into being and went extinct within a short period of time and are also found worldwide. Once established, scientists use index fossils to date other neighboring fossils when datable igneous rocks are not locally present. Until Swinehart’s recent discovery, the Phoebodus sophiae appeared to be a good candidate for a proxy index fossil— a proxy stands in when no traditionally established index fossil is present. Though slightly less accurate, a proxy still allows scientists to place a fossil’s date with relative certainty.
The complicating fossil is now located in the Hillsdale’s very own Daniel M. Fisk Museum of Natural History right next to a life sized model of Phoebodus sophiae that Swinehart himself created—rather unconventionally.
“I am a rather frugal individual and some of the materials used to sculpt things are quite expensive,” Swinehart said. “I mushed aluminum foil into the general shape, I wrapped it in masking tape, then I used notecards for the fins and a two part sculpting epoxy to cover it.”
He topped off his discovery with an orange rubber anemone he purchased from Walmart for $2.50 to represent a living horn coral.
Swinhart and his research partners will continue updating the museum exhibit with any new discoveries and data they find.