Entombed in Calvert Cliffs: Fossilized Behaviors from the Miocene Era
An Interview with Stephen Godfrey
By Lindsay Wooleyhand
Originally appearing in Slackwater, Volume 8
Dr. Stephen Godfrey, a native of Alberta, Canada, has lived in Southern Maryland and worked at the Calvert Marine Museum since 1998. The current Curator of Paleontology for the museum, he discusses what Southern Maryland looked like during the Miocene Epoch and the significance of his working relationships with the local paleontological community in the following oral history excerpts.
Collect, preserve, and interpret the local fossil resource: as the Curator of Paleontology, that is my mandate. One of the parts of this job that I find so exciting is that when I’m presented with fossils, I am sort of like C.S.I. My job is to extract as much information from those fossils as possible, so it’s my task to help the fossil tell its story. I’m kind of the mouthpiece for the fossil, and I love being able to do that.
“What we want to do is recreate.”
Initially, when Calvert Marine Museum was formed, paleontology was one of the three principal disciplines that was taught, along with maritime history and estuarine biology, because of the presence of Calvert Cliffs. There’s roughly ten million years’ worth of earth’s geologic history preserved in the sediments that compose the cliffs, dating between eighteen and eight million years ago. These sediments are the eroded remnants of the Piedmont and Appalachian Mountains. As the mountains were being eroded in prehistoric times, these sediments were carried by river into the Atlantic Coastal Plain, where they were then deposited on the bottom of the Atlantic Ocean. They’ve been raised a little bit, making these cliffs exposed.
These sediments that make up the cliff are not cemented together; they’re not naturally hardened. They’ve been compressed, so they hold their shape—you can walk up to the cliff face and just start digging through the sandy, silty sediments with your fingernails. Since they’re not really indurated by a natural chemical reaction that would have welded the particles together, the waves then pound against the base of the cliff and erode [its] face. Eventually, these sediments will just slough off, [and] they’re filled with fossils.
Imagine [it] as a giant layer cake that goes all the way into Washington, D.C., but as you get closer to Washington, the layer cake gets narrower and thinner, sort of like a giant wedge. Out here [in Southern Maryland] it’s a couple hundred feet thick [and] filled with these sediments. As those sediments [fall] away, the fossils that are entombed become exposed and, if they’re not excavated, fall onto the beach [where] people can collect them.
People are mostly interested in the fossil shark teeth, but we’re interested in everything else—all other different kinds of fossils. What we want to do is recreate; we want to tell the story of what it was like here in the Miocene Epoch. The term Miocene refers to a certain period in earth’s geologic history that lasted from about twenty-five million years ago to about five million years ago. Calvert Cliffs presents a small segment of that time, from about eight to eighteen million years ago, so about ten million years. Using that fossil resource, we want to describe, as much as possible, the diversity and abundance of the plants and animals that were present at that time. During the Miocene Epoch, on average, temperatures were several degrees warmer than they are today. So, the climate here in Maryland would’ve been more like it is in the Carolinas and Georgia. There was no ice at the North Pole, and, on average, there was less ice at the South Pole. If you melt those polar ice caps, you invariably raise the water [levels] in the oceans. For much of the Miocene, then, Southern Maryland would have been underwater. We would have had mollusks around us on the ocean floor.
We would have had sharks and fish, sea turtles [and] sea cows, all kinds of dolphins and whales and, of course, the megalodon—the giant, white shark. They all would have been living in that water, which means this is a marine environment that we’re sampling when we collect fossils along Calvert Cliffs.
That’s not to say there aren’t some fossils of land animals; [those] fossils that we find in this environment were probably carried by these rivers. Let’s say a prehistoric elephant or rhino was drowned as it tried to ford a river. Its carcass would have then been carried out to sea and, as it decomposed, different parts of the body fell to the ocean floor. Those parts then would have been entombed in the sediments, which continued to build up and contribute to those layer cake-like sediments that we now see exposed along Calvert Cliffs. Anything that survived in those sediments that could [have] fossilized is what we collect in order to create an understanding of what it was like in the Miocene.
"I'm kind of like the mouthpiece for the fossil, and I love being able to do that."
Stephen Godfrey
We particularly like to collect any bony fossils [that] are found along the cliffs. If it has a bite mark on it or it’s pathological—it has something wrong with it—that’s very exciting because we’re interested in what those tell us about trophic interactions. Finding a fossil that has a shark tooth embedded in it, or tooth impressions, shows you those real-life interactions. In a way, it’s a fossilized behavior. Those fossils are capturing the moment, the behavior of that shark interacting with it, because of the fact that it bit it.
I would have to say the most memorable fossil that has ever come into my office was a coprolite, which is the technical term that we give to fossilized feces. You wouldn’t think that a coprolite could be very interesting, but this coprolite, which is about the size of your fist, has shark tooth impressions in it. This means that at some point in the life of that fecal mass, a shark bit it and left tooth impressions. I mixed up a molding compound, and I poured it into the impressions. When it cured, I peeled it off [and] was able to see the shape of the teeth that penetrated the fecal mass; from the shape of the teeth, we could tell it was from one of the extinct tiger sharks. Scientists know from modern tiger sharks that they will bite things to assess their palatability; “Is this something I want to eat?”
[Do you think that tiger shark ate the feces?]
No, it didn’t. It was in its mouth, but not entirely, and after it bit it, it decided, “Maybe I’m just not that hungry.” So, the coprolite sank to the bottom of the ocean, became entombed in sediment, and then twelve million years later, it was found by an amateur collector, Douggie Douglass. He often parks along the side of the road and sells fossilized shark teeth. You know, when he brought it into my office my brain was like, “I cannot believe what I am seeing!”
Fossilized Behavior - The deepest bite impressions on the coprolite, courtesy of what’s believed to be the prehistoric tiger shark (2010)
We don’t know what animal produced the fecal mass. Most paleontologists usually attribute coprolite to crocodiles, because modern crocodiles apparently make very dense feces, which means there’s a better chance of it holding together and being preserved. You know, what’s the probability of feces floating in the water or sitting on the bottom of the ocean, and a shark biting it, and it being preserved? Since I published about the coprolite, people have contacted me about similar specimens that are in private collections, which means there are more out there. It’s an example of something that you would never imagine being preserved; that’s why it is so memorable.
The other part of the story is that the tooth impressions did not equally penetrate the feces on the top and the bottom. I wondered why that would be. I mean, maybe it was just serendipity with the way the shark mouth bit the fecal mass. When I tell the story in a slide presentation, I show an image of a Miocene marine crocodile being plowed into by a tiger shark, because maybe the difference in the way the teeth penetrated the feces has everything to do with it still being inside the abdominal cavity of the crocodile. We know that modern tiger sharks are voracious predators, so it might’ve bitten into it and then it let go. Maybe the initial attack was to kill or dismember the crocodile and then, for some reason, the section of the intestines that had the feces in it wasn’t consumed. So, it sank to the bottom of the ocean and became fossilized. I can’t prove either theory because the evidence doesn’t conclusively allow me to do that. I can’t show that that is what happened— that the feces was floating in the water and the shark bit it, or the feces was on the ocean bottom and the shark bit it. As a paleontologist, though, I’m a bit of a storyteller, so I can tell these stories and open up the numerous possibilities.
You would think that after people have collected here for almost two hundred years, we would have exhausted the diversity. Obviously, it takes longer for Calvert Marine Museum to find new species, but every year we find new kinds of creatures that we then get to describe and name and introduce to the local population. Our intent is to disseminate this knowledge as widely as possible. We achieve our mission, in part, by accepting fossils from a large avocational and amateur community that love to collect—and, because we’re collecting [too], the collection is dynamic. It’s growing, and we have new things to talk about, write about, publish about, and make exhibits on. That, for us, is what makes this job really exciting.
One thing that you don’t learn in graduate school is how important people can be to a science. I’ve learned in my tenure here that the local amateur and avocational community are passionate about paleontology, and a lot of them want their collections to come to the museum. They recognize that we’re doing a good job at preserving these collections and, basically, we curate their collection for them. Many of them actually find fossils that are new to science; in fact, most of my publications are based on fossils that have been found by amateur paleontologists, like the coprolite Douggie Douglass found.
In fact, along Calvert Cliffs, we now know of more than thirty different kinds of dolphins that lived at different times during the Miocene Epoch, which is amazing! It’s one of the most diverse dolphin faunas known anywhere in the world, alive or dead. Many of those new kinds of dolphins were found by locals that I’ve had the privilege of being able to name species after, in their honor. It is always a pleasure to be able to name a species after someone who found it [and] donated it to us. These people are very passionate about paleontology and understand that they can make a significant contribution to this science. It’s one of the sciences where these people are very learned and can make significant contributions because they’re the eyes on the ground; they’re out there doing the work and collecting. They are also motivated because they want to be a part of this exciting endeavor.
I’ve found [it] really gratifying and beneficial to be able to work with this large community that’s going to do paleontology whether or not we do paleontology. I’ve been exceedingly blessed to work here at this museum and with this community. I mean, they say if you love what you do, you don’t work a day in your life, and that is true for me.
