Last month, on a sunny day on the beach, an intern with the Point Reyes National Seashore showed a paleontologist a cliff exposure where the fossil of a marine mammal skull, which she first spotted in May, was jutting out. The paleontologist recognized it as a dolphin fossil, a rare find because they are small.
The two started chipping away and realized it wasn’t just an isolated fragment. “We started to dig and kept going and finding more and more,” said Lillian Pearson, the paleontological intern placed in the park through a partnership with the Geological Society of America.
Besides the skull, they found the humerus, the mandible, the ribs and a few vertebrae. “He was really excited,” Ms. Pearson said of the paleontologist, Robert Boessenecker.
The fossil was buried at the base of a cliff in what’s called the Purisima formation, a layer of rock about seven to three million years old and visible in light-colored bluffs along Point Reyes. Partial skeletons, as opposed to isolated bones, “are not common in this formation, probably because currents on the seafloor carry smaller parts of skeleton away,” said Mr. Boessenecker, who has been working at the University of California Museum of Paleontology and was at the seashore on a research permit.
This particular fossil, in which a lot of the bones are still together, was a red flag for Mr. Boessenecker. “And by red flag I mean, we gotta dig this thing up,” he said.
They chiseled out a two-foot-long portion of rock encasing the fossil and applied 80 pounds of white plaster to protect it. They left it overnight because of blustery weather and returned the next day to retrieve it, dragging it partway down the beach on a piece of driftwood.
The dolphin fossil, about 30 percent complete, has tiny conical teeth, a short snout and is, in all likelihood, a new and unnamed species. The discovery and excavation of the piece—which still has to be fully cleaned before scientists can determine if it is an new species—arose from two projects in the park, one of which is an effort to monitor fossils encased in the seashore’s crumbling cliffs.
Ms. Pearson has been at the seashore since March under the auspices of the National Park Service’s Geoscientists-in-the-Parks Program with the goal of creating a fossil monitoring program. She is surveying Point Reyes beaches to choose which spots—perhaps a couple dozen—might hold particular importance.
Those areas will eventually be monitored and, when fossils are sufficiently exposed, excavated.
Once the monitoring program is in place, park staff or volunteers could check the areas of highest interest, perhaps annually or every couple years.
“This is the first time that there’s been a concerted effort to document what’s here,” said Ben Becker, a marine scientist at the seashore and head of the park’s Pacific Coast Learning Center.
Securing a paleontological intern was contingent on the Geoscientists-in-the-Parks program considering Point Reyes a high-priority area. The seashore’s coastal cliffs—consisting in many places of crumbly sandstone—help make that case. Relentless coastal erosion both exposes the fossils, making them possible to see, and threatens them.
“Especially with sea-level rise increasing storm frequency and those sorts of things, as we lose our cliffs, we could lose important fossils for [cataloguing] undescribed species or reconstructing evolutionary history,” Mr. Becker said.
Mr. Boessenecker obtained his second research permit this spring to work at Point Reyes. The seashore’s marine mammal fossils, he said, are not as well documented as those on other areas of the West Coast.
“By and large, no one’s really gone and done a serious paleontological effort” of marine mammals in Point Reyes, he said. He believes he has a “high chance” of finding significant specimens; in 2011, on his first stint, he collected fossils of a 10-foot long saber-toothed dolphin, the ear bones of a porpoise and pieces of dwarf baleen whale bones.
“It didn’t take a whole lot of digging” to find them, he added.
Finding fossils in the cliffs is important because they are “in situ,” or situated in geologic time, said Ms. Pearson, who has spent the last two years traveling to places like the Panama Canal on excavating missions. “So we can figure out, ‘Okay, this is older than this one.”
Other fossils, called float fossils, have broken away from the cliffs to the beach, and can be more difficult to date.