The Chesapeake's Excellent Fossils
Discoveries in Bay cliff formations are yielding new insights into prehistoric creatures, including ancient whales
Calvert Cliffs, seen here rising from the Chesapeake Bay by Rocky Point, are a scenic landmark. Photograph courtesy of Stephen Godfrey, Calvert Marine Museum.
NEARLY 14 MILLION YEARS AGO OFF THE ATLANTIC COAST, an ancestor of today's whales died. It might have been attacked by a predator or simply succumbed to old age and disease. Either way, the whale sank 100 feet or more to the sea floor below. There, it provided a feast for scavenging sharks and microbes.
Over time, mud and sand trickled down to the sea floor, burying the whale from head to fluke. It wouldn't be seen again until July 2013, when an amateur fossil hunter spotted what looked like a jawbone poking out of a cliff face on the shores of the Potomac River.
Stratford Cliffs straddle the Potomac along a short stretch of Virginia's Northern Neck. At their peak, they rise to more than 100 feet high. Jon Bachman had been searching for sharks' teeth and other fossils on the beaches below those cliffs when he stumbled across the fossilized bone. The large mandible was just visible in the tan cliff face.
Fortunately, not far away lived a paleontologist with a long-time interest in the cliffs, and he knew what to do next. Stephen Godfrey, the curator of paleontology at the Calvert Marine Museum in Solomons, Maryland, began the excavation of the jawbone — which turned out to be much more. Over several weeks, the team, which included a host of volunteers, unearthed from the cliff face an entire whale skull, measuring six feet from front to back. Along with it came many other bones: vertebrae, pieces of ribs, a humerus from right below the whale's shoulder, and part of a flipper bone. For paleontologists, to find so many fossilized pieces of a single whale in one place constituted a bonanza.
The leviathan's remains may seem like an unusual thing to discover around the Chesapeake Bay, but the region has long been known for producing plentiful fossils of marine life, including whales. Most have come from the Calvert Cliffs, located in Maryland about 25 miles northeast of the Stratford features.
Part of the same geologic formation as the Stratford features, Calvert Cliffs run 30 miles down the Bay's western shore, beginning near the town of Chesapeake Beach and ending by Drum Point on the Patuxent River. The cliffs — which turn golden during sunrise — and their surrounding beaches in Calvert County are known for fossilized sharks' teeth and other prehistoric remains. Look closely, and you'll find an explosion of life recorded in stone: whale fossils, yes, but also ancient sand dollars, pecten scallops, and twisting shells from sea snails. These animals all lived during a geologic epoch called the Miocene, which lasted from about 23 to five million years ago. It was an important period in the evolution of whales.
Many people might consider those leavings mere souvenirs, but for paleontologists, the cliffs along the Chesapeake rank among the most important research sites in the Mid-Atlantic region. Fossils found here have certainly contributed much of what we know today about the planet's Miocene seas. For generations, scientists have walked the cliffs, building a better and better picture of what those ancient oceans would have looked like: what creatures plumbed the oceans millions of years ago, and how did they live? The evidence there has even helped scientists understand why some modern whales lack a sense of smell.
"Okay, that was a good day," says scientist Stephen Godfrey (top), holding a fossilized whale backbone that's been wrapped in plaster. He spent much of his morning carefully digging around this fossil (middle), which was found at the base of Stratford Cliffs in Virginia. This fossil, like others found along Stratford or Calvert Cliffs, dates back to the Miocene epoch (see time scale above). This geologic epoch was important in the evolution of whales. Photographs, Daniel Strain; time scale adapted from a USGS graphic.
When it comes to the history of life on earth, the Chesapeake's cliffs are "particularly good at telling part of that story," Godfrey says, "allowing us to get a really good picture of the diversity of organisms and what they looked like."
On a sunny October morning, the beach where Bachman discovered the latest of the Bay's famous fossils this past summer is quiet. Only Godfrey and a volunteer, a long-time fossil hobbyist named Marco Gulotta, are working here today. The two have returned to this sandy spot in Virginia to dig for parts of the whale that had been left behind when the skull was originally removed.
The nearby Potomac River is as smooth as gelatin. Godfrey, wearing waterproof waders and a flannel shirt, is crouching down in front of a waist-high hole in the sand-colored cliff face. He and Gulotta had recently carved out this small cave, using a gardening hoe and screwdrivers to chip away at the soft, clayey sediment.
"Now at the back of the hole, you can see the brown bone back there. That's a vertebra," Godfrey says. "That's our goal for the day."
The backbone, which is about the width of a basketball, looks solid now, but Godfrey will need to be careful getting it out. After having been buried under sediment for millions of years, fossils like this one often fall apart into many pieces when picked up, Godfrey explains. To avoid that, he will scrape gingerly around the fossil, exposing all of its sides. Then, he'll cover it in bandages coated with plaster — the same bandages that doctors use to mold plaster casts for broken bones. That should keep the vertebra together.
For Godfrey, the work of extracting this bone — and the patience it will require — are worth it. "For me, at the heart of this is an amazing object," Godfrey says. "I want to know what it is, and I want to extract as much information as I can."
In that sense, he's far from alone: Calvert and Stratford cliffs have long been a valuable resource for scientists hoping to extract information about the planet's prehistoric seas. The first fossil from here to pop up in the scientific literature was the shell of a sea snail, illustrated in a 1770 natural history tome, according to the Maryland Geological Survey. And as the catalog of fossils collected from the cliffs grew over the centuries that followed, scientists gained a more complete understanding of life during the Miocene epoch.
The span of time may lack the cultural cachet of other periods like the Jurassic when dinosaurs roamed the earth. But the more scientists learn about the Miocene, the more they are able to grasp its importance in the evolution of many marine organisms.
Those organisms would have swum or rested in salt water that was much warmer than are today's oceans, scientists say. Because of high sea levels, a stretch of the Atlantic Ocean, called the Salisbury Embayment, extended far inland over the East Coast, all the way to where Washington, D.C., currently stands. Crocodiles, dolphins, and sharks the size of school buses flourished in this muggy environment.
New species of whales emerged during this period, marking the transition of the species from animals that had one "fin" on land and the other in the water to true ocean mammals. Biologists use the term "radiation event" to describe the rapid appearance of several new species from one or more ancestors.
"You're right on the cusp of where you went from Archaeocetes, those are some of the very early whales," says Ralph Eshelman, a paleontologist and the founding director of the Calvert Marine Museum. "And you begin to have this vast radiation where you're getting into the kinds of whales that you have today."
Much of that life is captured in Calvert Cliffs. To date, paleontologists, working for more than a century along the cliffs, have catalogued and named more than 600 fossil species of all types, including mollusks, sharks, birds, and of course, whales.
The journey of those remains from ocean to museum display case was a long one: like the Stratford whale, these organisms died and sank to the bottom of the Salisbury Embayment during the Miocene. As temperatures cooled toward the end of that epoch, sea levels around the globe fell, and the ancient embayment shrank away.
Over time, however, waters rushing over the area where the Chesapeake is now cut their way into that old sea floor, forming what became Calvert Cliffs. Today, this erosion continues to eat away at the precipices, causing the cliffs to recede at a steady clip. While that erosion presents perils to people who live nearby (see Saving Calvert Cliffs), it also continuously unearths new specimens for fossil hunters to find and catalog.
A fertile habitat for dolphins, sharks, and manatee-like mammals called dugongs, the Salisbury Embayment (top), part of the Atlantic Ocean, covered whole portions of modern-day Maryland during much of the Miocene. The sediments that lay at the bottom of the ancient embayment now make up the geologic formations visible in Calvert Cliffs (bottom), shown here in a generic cross-section of the outcrops. The cliffs are split into bands, or strata, made up of different types of sediment. Within each formation is evidence of fluctuations in climate. You tend to see more sands during cooler periods and more clay and silt during warmer ones. Illustrations above, redrawn by Sandy Rodgers from figures in Clark et al. 2004.
The cliffs, then, provide scientists with the means to look back through time, helping them understand how fossilized organisms from the Miocene fit into the broader history of life on earth. The key to doing that lies in the cliffs' geology.
If you look closely at the faces of the Calvert Cliffs, you can see distinct bands, or strata, bearing sediments in different colors running across the surface — Peter Vogt, a retired geologist who lives in Calvert County, likens the cliffs to a "layer cake." Those layers, in turn, also function like a sort of timeline.
It works like this: through decades of study, researchers have roughly estimated the age of the various strata in the Chesapeake's cliffs. One of the ways they have done that is by searching through the cliff layers to find "index fossils." In general, these fossils, which are often types of mollusks or single-celled organisms, are known to have flourished at only one point in the history of life on earth. That makes them a shortcut for dating geologic strata: if you find the right index fossil at a certain point in your cliffs, for instance, then you can roughly estimate the age of the whale skull sitting nearby.
Scientists have split the geology of Calvert Cliffs into three main groups of layers, or formations: the Calvert, Choptank, and St. Marys formations. The oldest of the three, the Calvert Formation, sits at the base of the cliffs. That's about where Jon Bachman found his whale. These layers reach back to about 18 million years ago and represent the Miocene at its warmest. Temperatures then were around six degrees Fahrenheit warmer than they are today.
By the time you reach the St. Marys Formation, the youngest of the bunch, the Miocene oceans had begun to cool. Those layers, found at the top of the cliffs, stop around eight million years ago, coinciding with the disappearance of many warm-weather-loving organisms from Maryland — why, perhaps, you don't see crocodiles around the Bay anymore.
Worldwide, there are few locales that carry such a long-running record of marine organisms in the Miocene, scientists say. In addition to the Calvert Cliffs region, paleontologists have also dug up rich veins of marine fossils in sea cliffs around Antwerp, Belgium and a set of desert outcrops in Peru. But Maryland scientists argue that their paleontological sites are the best: fossils found here have tended to be older than those from Peru and in better condition than fossils from Belgium. The cliff chain "really deserves being considered one of the most important geological localities on the East Coast of the United States," Eshelman says.
David Bohaska, a collections manager for vertebrate paleontology at the Smithsonian Institution's National Museum of Natural History, agrees. He first encountered the fossils of Calvert Cliffs on a seventh-grade field trip. "As a kid, reading about dinosaurs and such, you always think of the Gobi Desert or expeditions out west," says Bohaska, who grew up in the Towson area. "I'm a proud Marylander. It's kind of neat that my home state is, in fact, famous for some of its fossils."
The First Museum
Stephen Godfrey, who joined the Calvert Marine Museum in 1998, has probably done more than anyone in recent years to find new information about those famous fossils. And just as his fossils undertook a long journey before reaching the museum, so did he.
Today the modest scientist works out of an office near the museum's main exhibit hall by the water in Solomons. The room is a testament to his love of natural history. On the walls and shelves are paintings of melting glaciers and a model of a Brachiosaurus skull — all pieces made by the scientist, who moonlights as an amateur artist and sculptor. On his way in, he affectionately pats the head of a model of a baby duck-billed dinosaur that's knee-high and painted green. "This was my first," he says.
iStockphoto.com/University of Texas Map Library
That love of piecing together animals started early. As a child, Godfrey became taken with the idea of founding his own museum.
"My bedroom was transformed into a museum: seashells, insects, anything. Fungi, whatever I could collect," Godfrey says. "I would label all these things. My room, I kid you not — I had things hanging from the ceiling."
He particularly liked skeletons, finding the raw materials he needed to build his own from road-kill specimens: raccoons, dogs, and other assorted animals. Using glue and wire, plus a textbook of animal anatomy loaned to him by his uncle, Godfrey would meticulously rebuild the animals' injured skeletons — bringing the creatures back to life. Sort of.
But the budding scientist's upbringing initially steered him away from a career in paleontology. Godfrey, whose parents were devout Christians, was raised as a young-earth creationist. For much of his youth, he believed that the world was only a few thousand years old and rejected the science of evolution. When he became a graduate student in paleontology, it wasn't to dig up dinosaurs but to evaluate for himself whether the evidence presented for evolution in textbooks had merit.
But Godfrey got lucky: as a student, he was invited on a paleontological expedition to a quarry in Kansas. There, members of the expedition uncovered numerous slabs of rock that still bore the footprints of prehistoric lizards that lived during the time of the dinosaurs. "We came upon these little imprints, and, for me, it was just earth-shattering," he says.
The scientist, who now talks passionately about the deep history of life, still keeps one of those rock slabs in a file cabinet in his office. He takes it out and traces the imprints, no bigger than what a pigeon would leave behind, with his fingers. "You can see the little toes," he says. "Front foot, back foot."
Oceans of Whales
These days, the former creationist isn't dabbling in dino footprints. But his work around Calvert Cliffs has given him the chance to help build on what scientists know about the history of life on earth — albeit a small bit of it.
He's thrown himself especially into the study of whales. And for good reason: near the middle of the Miocene, there were more species of whales alive than at any other time, including the present. The creatures' success likely comes down to warm ocean temperatures, says Olivier Lambert, a paleontologist specializing in whales at the Royal Belgian Institute of Natural Sciences in Brussels. The balmy conditions seen during the Miocene would have supported huge schools of fish and other whale food.
And at the time, new species of whales were emerging, while older ones were drifting toward extinction. Long-snouted dolphins, small whales with unusually long snouts, for instance, can be found in Calvert Cliffs' older layers. But as you move forward in time, they slowly dwindle, then disappear entirely for reasons that are still unclear.
On the flip side, most of the modern families of whales that we see today arose during the Miocene. The epoch saw the first relatives of modern dolphins, porpoises, beaked whales, and narwhals. The Rorquals, a family that today includes blue whales, and right whales also came into existence around this time.
In all, scientists have catalogued and named 28 species of fossil whales found at Calvert Cliffs, marking different periods in the evolution of these creatures. Today, only around 80 species of whales swim the seas worldwide.
Now, one of the challenges facing Godfrey and his colleagues is to identify a single fossilized whale — the one found by Jon Bachman in Virginia.
For now that specimen — owned by the foundation behind Stratford Hall, the historic estate where the whale was found — is being kept at the Calvert Marine Museum. Having run out of space in his lab, Godfrey installed the skull in one of the museum's exhibit halls. It's next to a wall-sized display illustrating the entire history of life on earth.
The skull is lying upside down, with the roof of its large maw visible to guests passing by. In life, this whale might have stretched out to around 25 feet long. That puts it at about the same size as a modern-day minke whale. At this point in the Miocene, Godfrey says, whales had yet to hit the mammoth sizes of species alive today like blue whales. Shrimpish or not, the skeleton is remarkable, in large part because of its completeness. Usually, when whales die, their bones are scattered across the sea floor, making them difficult to dig up in one piece. The find isn't the most complete of Godfrey's career. But it's close.
Volunteers at the museum have already begun the painstaking process of "prepping" what's left of it. Using paint brushes and dental scalers, they will slowly dust and scrape the mud and clay away from the animal's skull, leaving only the coffee-colored fossil behind.
As the skull emerges from the muck, Godfrey's work will begin. "As we prep the skull, the initial task will be [to ask] what kind of whale will it be," he says. "It's probably a known form, but we don't know that for sure. There's a slim chance that this is a new kind of extinct whale."
Even without a name, Godfrey can still glean valuable information about how this animal might fit into the evolution of whales. Based on where it was found in the cliffs, for instance, Godfrey's team estimates that this specimen is about 14 million years old. It was also a "baleen" whale, a group of animals that exist today and include blue, humpback, and gray whales.
These creatures are known for taking a diverse approach to eating, Godfrey says. Some, like blue and minke whales, feed by way of their gaping mouths. As they swim, they open up, capturing schools of krill and other small organisms. Gray whales, on the other hand, go for creatures living in the mud. Using their tough heads, they rake the ocean bottom, slurping up a host of burrowing organisms.
Based on the anatomy of its skull, however, the Virginia whale doesn't seem to fit cleanly into either category, Godfrey says. He suspects that this animal may represent a mid-way point in the evolution of whale dining. The members of this species were "a little bit like gray whales, but they were heading toward what blue whales were doing," he says.
For a paleontologist with a deep love of evolution, knowing how ancient animals lived is a big part of the fun.
"If you can describe a fossil, name it, that's fun. But if you can tell more of the story, that's kind of the bonus," Godfrey says. "Who doesn't like a good story?"
A collector's dream, the Chesapeake's eroding cliffs have unearthed a variety of ancient species, as these examples show. What looks like a trough of dirt (top left) is actually a "field jacket" containing a fossilized whale skull found earlier this year in Stratford Cliffs. Curators are slowly cleaning the skull. Other species include a crocodile (bottom left) and a now-extinct long-snouted dolphin (top right). No creature has captured the imagination of non-scientists quite so much as the megalodon, a hulking shark that could grow up to about 60 feet long. Lucky fossil hunters can still find the shark's teeth (bottom right). On the small end of the scale is the sea snail belonging to the genus Ecphora (bottom middle). Photographs courtesy of Stephen Godfrey, Calvert Marine Museum.
A Nose for Whales
Right now, there's a whole story laid out around his office. This one has to do with a less well-known piece of the evolution of whales — how some lost their ability to smell.
To tell that story, Godfrey points to a series of animal skulls around his office. Some of the skulls are from fossil animals, but others came from modern ones. There's a cow skull, one from a moose, and another from a modern bottlenose dolphin.
Godfrey picks up one of the items. This skull, taken from a deer, has been sliced right behind where the creature's nostrils would have been. The cut lets you look back into the animal's nasal passages. "You can see the turbinates," Godfrey says, poking his ballpoint pen into the deer's nose, "very thin, scroll-like bones."
And, indeed, jammed behind the nose, there's a collection of twirling bones. End-on, they look a bit like old parchments stacked on a shelf. These fragile-looking structures were critical to the deer's sense of smell, Godfrey says. After inhaling, odors would have pooled around these bones, allowing the animal to pick up the smells.
You might not think that whales, which spend most of their lives underwater, can smell at all. But some living whales, Godfrey notes, have similar structures inside their own nasal passages. That indicates that they can also smell the salty sea air. In particular, it's the baleen whales, like the species collected from Virginia, that seem to be able to take a good sniff.
But another group, called toothed whales, can't smell. They don't need to. Unlike baleen whales, these mammals, which include dolphins, sperm whales, and narwhals, hunt fish and squid using the equivalent of sonar — they listen to how noises bounce around in the environment. That trait, shared by bats, is called echolocation.
To explore when toothed whales lost their ability to smell, Godfrey came up with a new technique for using a CT scanner to measure various structures in the skulls of fossil whales. To start off, he examined the skull of a roughly 16-million-year-old toothed whale — called a Squalodon — that had been found high up in Calvert Cliffs. The creature, it turns out, still had the remnants of turbinates buried in its nasal passages, Godfrey says. And that suggests that it, too, could take in aromas.
By the time bottlenose dolphins emerged around the globe in relatively modern times, however, those structures had disappeared entirely. "In the Miocene, we actually see the loss of the sense of smell in toothed whales," he says.
To tell that story, Godfrey points to a series of animal skulls around his office. Some Baleen whales, on the other hand, never lost their ability to smell, Godfrey says. In fact, according to his research, the structures involved in their sense of smell remained largely unchanged over tens of millions of years of evolution. The fact that these whales hung onto their smell structures for so long suggests that they needed that anatomy to survive, Godfrey says. And they're likely still putting their sense of smell to good use today.
Scientists working with modern whales have reasoned that these animals may be using their noses to follow schools of krill and other organisms. These stinky crustaceans are known to give off a slight odor — it is part of the smell that most people associate with the ocean, says Godfrey. "Just like a wild animal, a raccoon, opossum, a dog, can follow a scent... baleen whales seem to be doing the same thing," he says.
The paleontologist and his colleagues published their findings on whale smell in two papers in 2013 in the journals The Anatomical Record and Comptes Rendus Palevol.
Olivier Lambert, the Belgian paleontologist, notes that scientists had long known about the diverging senses of smell in baleen and toothed whales, "but what Stephen did is he tried to quantify this," he says. "And this is a nice advance in the field."
Growing a Backbone
Back on the beach in Virginia, Godfrey is almost done extracting the whale vertebra. Stowed in its plaster "field jacket," the find should be safe to move now. Giving a grunt, the paleontologist rolls it out of its hole, all in one piece.
Godfrey's day of digging may be over, but he knows that paleontology around the Chesapeake's cliffs will continue for decades. Long after Godfrey is retired, researchers will continue to improve the picture of how animals like whales evolved during this one period in prehistory, fossil by fossil. "If we keep finding new stuff, keep finding new fossils," he says, "then we have a much better chance of... moving paleontology forward and describing in greater detail the diversity of animals that were here before us."
On his way out, the paleontologist hoists the heavy fossil into his knapsack, then heads down the beach, carrying it on his own back — one more small piece of a much, much bigger story.