This year is David Bohaska’s 50th anniversary. Not for his wedding — he and his wife are just celebrating their 30th — but for when he found his first fossil, a shark tooth.
“It started on a seventh-grade field trip and I got hooked,” Bohaska, a museum specialist at the Smithsonian Institution, told me of his fossil-hunting passion while we sat in the bowels of the Natural History Museum in Washington, D.C., among rows of ancient bones in protective cases and cabinets holding drawers upon drawers of carefully categorized fossils.
Bohaska still has that first mako shark tooth found at Calvert Cliffs State Park in Lusby, Maryland, because “back then I kept everything.”
Nearly 30 years after Bohaska found his first tooth, third-grader Eric Hillman was visiting Calvert Cliffs as well. He waded into the deeper water, thinking that the farther out he went, the larger the shark teeth buried below could be. He scooped up a handful of sand, brought it back to the dry beach and spread it out, sifting through the pebbles looking for his treasure.
“When I found that first shark tooth, you almost had to take a second look at it,” he said.
Like Bohaska, Hillman was also hooked on fossil hunting in that moment. Bohaska would go on to become an expert, specializing in marine mammals and marine life, and working at the Smithsonian for the last 25 years; Hillman would maintain an amateur passion and to this day plans to go cage-diving with sharks to “see how powerful they really are down there.”
I learned of Eric’s shark tooth collection the first time I “met the parents.” He’s my husband. He would later tell me that he knew I was a “keeper” when I didn’t freak out or laugh upon seeing his “nerdy” collection. As someone who created a pretty extensive insect collection for an entomology class myself, which involved killing many of them in fumes of ethyl alcohol for later positioning and pinning, I was unfazed. Years later, after we were married, his parents decided to divest themselves of Eric’s childhood keepsakes, putting them into our care. Now that the shark teeth reside in my own apartment in the D.C. metro area, I decided to take some of these pieces of history to the Smithsonian for evaluation and get my own inside look at their own collection, not to mention glean some tips for how the average person can find their own shark teeth and other fossils.
‘Shark Teeth Are More Complicated Than You Might Think’
When I opened the wooden display box and unwrapped the shark teeth — carefully packaged in preparation for my ride on the D.C. metro transit system — in the storage and office facility below the main exhibit halls of the Natural History Museum on Wednesday, Bohaska immediately identified most of Eric’s teeth as Carcharodon megalodon, which you might recognize by its common name: megalodon.
The museum’s ocean exhibit hall contains a reproduction of what scientists think a megalodon’s jaw would look like, based on the structure of a modern shark. When we trekked up there to check out the jaw that an adult could comfortably stand inside, Bohaska explained that the first row of teeth on the top and bottom are real fossils while the rest were created from molds. He also noted that experts now think the shark, which scientists estimate lived 2 million years ago, would not be able to open his jaw quite so wide as the example in the museum.
Eric said he didn’t find any of the extinct megalodon teeth on his childhood hunts, but saved up his lawn-mowing and snow-shoveling money and purchased them.
The other three teeth in the display case, which Eric did find on one of his trips to the Calvert Cliffs in Maryland or in Venice Beach, Florida, Bohaska said, were from sharks known as Hemipristis serra, or snaggle tooth sharks.
Large fossils of sharks are rare finds due to their cartilaginous skeletons, which are likely to decompose before they can become fossilized over time. This is why shark teeth fossils are often found loose and not in a jaw. It’s also why, Bohaska said as we sat at a table with a reproduction of a prehistoric alligator jaw off to our right, there have been issues in the past with identifying sharks based on tooth specimens.
“Shark teeth are more complicated than you might think,” he said. “Upper and lower teeth can be different, front to back, and depending on the age of the shark, the teeth can change.
“And in the old days … with fossil sharks, they’d find a new tooth and they’d name it a new species,” Bohaska added, explaining that while the teeth might look different they can, in fact, come from the same species.
But “that’s the nature of science,” Bohaska shrugged.
“We’re never 100 percent ‘this is it,’ and I’m sure years from now people are going to think things that I wrote were garbage,” he joked.
What makes a find important enough to keep in the Smithsonian’s collection these days, Bohaska said, is if it is rare or it is found “in situ,” or the surrounding substrate. This would allow scientists to glean more information about the fossil, based on its location in the sediment and what was around it.
“To us, the information that comes with a fossil, in most cases, is much more important than the actual fossil itself,” Bohaska said, adding that it’s the stratigraphic level, which can help them identify geological time, and its location that help give the fossil a larger context.
Later, while we were walking up and down aisles of quarter cabinets, Bohaska pulled out dozens of drawers to show me just some of the thousands of shark teeth and vertebral centra, the disks that make up its equivalent of a spine.
Why keep so many specimens in their collection if they’re not for display? Several reasons, according to Bohaska.
First, the museum is obligated to keep a collection if it has been part of scientific research while in their care, just in case someone ever wants to re-evaluate the study or conduct other analysis. Other factors for keeping multiple examples from the same species include possible variation within the species and just in case destructive analysis has to be conducted. The latter is when researchers have to drill, cut or cause other damage to analyze specimens. Having multiple examples allows the museum to facilitate such research when necessary while still having intact fossil examples.
Hunting for Your Own Shark Teeth
There are several places around the country where fossilized shark teeth can be found, but Bohaska has some specific tips for amateur hunters.
He suggested people go out at low tide because areas that are at other times less exposed will be out of the water.
When he heads out to hunt for fossils — he went twice just this past weekend living near the Calvert Cliffs, prime fossil-hunting grounds off the Chesapeake Bay — he said he looks in gravel, rather than shells, though cool fragments can certainly be found in shell debris as well.
For the Calvert Cliffs, specifically, Bohaska said “the great secret” is to go after a few days with a northwest wind because it “blows water out of the bay,” meaning fresh fossils could have tumbled town with it.
Most shark teeth fossils have turned a brown or black color, so be looking for that rather than white. The color is the result of minerals they have been exposed to over time.
It can take some time to get the hang of finding shark teeth.
When I went shark tooth hunting once with Eric, I found zero teeth while he found three. Bohaska suggested someone with an already trained eye who finds a tooth should mark the area with a circle and tell others who are still learning to try to find it within that marking.
When it comes time to measure your shark teeth, the “official Smithsonian way,” Bohaska demonstrated, is to hold the tooth upright with its base at the bottom, with the tip in the air. Measure with a ruler from the base straight up to the tip.
Enthusiasts, like Eric, find shark teeth so fascinating because ”you always feel like you’re holding a little piece of history, like you’re holding a dinosaur,” he said.