Welcome to This Wild Life, a monthly feature from The Nat that highlights some of the Museum's scientists and staff and their work to study and preserve the biodiversity of our region.
Each day, visitors come to the San Diego Natural History Museum’s Paleontology Center and travel back in time millions of years—to a Southern California where creatures like mastodons roamed and marine life thrived in waters that covered much of our city today.
Every fossil at the Museum tells a story. But how did they end up in The Nat’s collection?
Most of the more than 1.6 million fossils that are housed at the Museum were found and prepared by The Nat’s PaleoServices team, a group dedicated to monitoring active construction projects around San Diego County and searching for ancient remains of the plants and animals that lived here long ago.
“We are conserving a resource,” says Jesse Shelmire, the PaleoServices field manager. “These will be gone if we do not collect them. We are the last line of defense.”
Shelmire, like many staff in the Paleontology Center, has dreamed of a job like this one since he was a kid. He was 5 years old when he visited the Carnegie Natural History Museum in Pittsburgh, well-known for its dinosaur fossils collection, an experience that set him on a path of exploration and a desire to be outside as much as possible.
“Half my days are inside and I'm looking out the window wondering, ‘how do I get back out there?” he says.
It’s rewarding work. The PaleoServices team monitors a range of projects, from the construction of a Home Depot in Mission Valley and the creation of a bike lane in Kensington to a housing development in Otay Mesa. They typically work on about a dozen active projects in the field at a time and find fossils almost every day—prehistoric treasures hidden beneath our modern world.
There are 47-million-year-old shells and shark teeth found in the coastal Scripps Formation, and 20-million-year-old heavy fossil beds containing a range of specimens. There’s even a brontotherium from around 40 million years ago found in Simi Valley—the same animal that was discovered in Oceanside in late September.
Before the team begins monitoring an active construction project, they must assess the area's geology to determine its rock type. Shelmire says that most projects in sedimentary rock are bound to have some fossils, though different rock formations hold different outcomes.
The San Diego Formation in southwestern San Diego, for example, is rich in possible marine life, like shells, marine animal bones, and shark teeth. The more inland Otay Formation, on the other hand, holds remains from on-land animals such as oreodonts, which are distantly related to camels and llamas.
The team finds fossils through several modes, from collecting sandbags and screening large volumes of sediment to breaking rocks open with rock hammers. Construction crews also play a role; a bulldozer or scraper can easily unearth fossils well below the ground’s surface.
It requires optimism for what one might find—and an open mind.
“You can't go in and look for one particular thing,” says paleontological specialist Chanel Stinson. “Otherwise, you're gonna miss the bigger picture or the smaller details.”
Stinson, a self-proclaimed “field rat,” says that some days on a site may not generate as many fossil discoveries. In those instances, she likes to go search for more modern bones, like those of squirrel or road runner that recently died.
Once the fossils are excavated, they’re brought to the Museum, where the paleontology team sorts and tags the specimens. From there, the scientists determine what is worth keeping for the Museum’s collection based on their value for science and research—a process led by Curator of Paleontology Dr. Tom Deméré.
Shelmire says it’s not only the fossil itself that can help scientists learn more about the past. The location and context in which it’s found can also shed new light on an ancient species or ecosystem.
"A whale might not actually be as important as something much smaller if it's in a fossil bed where we have a ton of that whale species,” Shelmire explains.
Once a fossil is determined as a fit for the Museum’s collection, it enters the prep lab, where a team of volunteers and staff members are ready to clean and prepare it.
One of those people is paleontological specialist Amanda Linn, who has worked at The Nat for 10 years. While she considered herself a “dino kid” growing up, spending time digging in the dirt and hoping to find real fossils, over time she found a love of museum work.
Linn uses a mix of mechanical and hand tools, including some more familiar items like X-Acto blades and dental picks. She also uses precision tools like pin vises, along with air scribes that use vibration to move rock and debris—also known as the “matrix”—away from the bone. When a bit more force is needed to remove the matrix, she uses a good old-fashioned hammer and chisel.
Fossils found during construction projects don’t always come to the prep lab perfectly intact, and some need to be glued back together. Others may only be pieces of a once larger fossil, though Linn says she would rather have a fragment of a fossil than none at all.
"When fossils get impacted by the equipment, we call it the ‘scraper tax,’” Linn said. "As soon as they scrape over a fossil and take away a chunk of it, we lose that chunk, but they uncovered the fossil for us.”
Linn is currently working to prepare some 2- to 3-million-year-old marine fossils found in the San Diego Formation during a current California Department of Transportation project on Interstate-805 in South San Diego County.
Her favorite fossil to ever prepare was from an Archeocyons, a doglike canid species found near Otay Ranch that lived and hunted in North America more than 20 million years ago.
Some scientists in the Paleontology Center have certain specialties in the field, such as the micro fossils or the geology of San Diego. But for most all, the experience of working for PaleoServices is one of constant learning and discovery.
“It's been an amazing opportunity to work here and learn different techniques, especially working in the lab,” Stinson says. “Going from finding something in the field and then being able to see it all the way through.”
Construction Project in Otay Mesa Yields Exciting Fossil Discovery
The Dinosaurs (or Lack Thereof) of Southern California
See the Ancient Creatures That Might Have Been Beneath Your Feet
This Wild Life showcases ongoing fieldwork at The Nat and the people behind it. Join our researchers, staff, and partners as they slog through frog ponds, dig up fossils, and track down lost species—making conservation possible with each data point and discovery. From Southern California to the tip of the Baja California Peninsula, our team is quite literally the boots on the ground, working to preserve this amazing place we call home.
Posted by Maura Fox, Senior Communications Manager.
Subscribe to our blog. Receive an email once a week that recaps the latest blog posts about our research, exhibitions, cool science news, and more