AS FOSSILS ARE REVEALED IN THE FOOTHILLS, SO ARE THE MYSTERIES
Editor’s note: The announcement this summer that a vast collection of Miocene fossils had been discovered in the Mokelumne River watershed stunned scientists. Never before had the foothills yielded such a trove, stony evidence of extinct rhinos, mastodons, three-toed horses, giant camels and more. The story of this discovery is told here by Rich Hanner, former editor of the News-Sentinel of Lodi, which first published it in June. We realize this isn’t the typical content for our Foothill Conservancy newsletter, but it helps to expand our understanding of the natural history and continuing evolution of this place we love.
Rich Hanner may be reached at email@example.com.
This is Part Two – Part One was included in the Fall 2021 eFocus
By Rich Hanner
Russell Shapiro, a paleontologist and geology professor, and an expert hunter of fossils, was stunned.
He’d spent the day scouring the foothills, assessing a site reportedly holding petrified wood and fossils.
“We knew right away: This was a significant discovery,” he said.
It was, in fact, a vast buried menagerie. Most of the fossils were from megafauna, huge beasts such as mastodons and camels and horses. But the trove, Shapiro saw, was incredibly diverse. There were remains of a bird, of tortoises, of a fish.
“Is was just mind-blowing,” he said. “And I knew we were just scratching the surface.”
The site is in a remote part of the East Bay Municipal Utility District holdings, not close to a road or trail, and it is not being publicly revealed.
Yet, by the time Shapiro arrived, looters had already made off with an agatized length of petrified wood.
It would be a race, in a way, to secure the site and others that would be found nearby, organize a major dig, and remove the best of the bones.
The initial discovery had been made, one of the most notable in the history of California.
But there was much work ahead. The mysteries, really, were just starting to unfold.
Hound on the hunt
Shapiro was led to the location by Greg Francek, an East Bay ranger who a few weeks before had found and unearthed a chunk of petrified wood.
A caver and naturalist, Francek was like a hound on the hunt. He returned to the area day after day, including his days off, uncovering a petrified forest that would eventually include more than 600 trees.
About three weeks in, on Aug. 7 of last year, he found not wood but bone. It was the fossil of a still-unidentified vertebrate; that is, a creature with a backbone.
Francek studied earth science at Columbia and American River colleges. He’d gleaned a boots-underground understanding of geology as the former manager of the Black Chasm cavern in Amador County.
He knew what he was uncovering could be big. His supervisors at East Bay agreed, hiring the consulting firm of Environmental Science Associates (ESA) to help investigate the discovery.
Enter Shapiro, professor at Chico State, and a member of ESA’s scientific team.
An affable sort with a quick wit, Shapiro is renowned for his knowledge of California prehistory.
He loves nothing more than getting his fingernails grimy at a dig.
“Going after fossils is a blast. It’s like being a hunter, but you don’t have to kill anything,” he said.
Piecing together fossils is a mix of hard science and well-informed speculation, he said. It’s often not clear, at least at first, what kind of creature a fossil is from, where it originated, or when it lived.
“Some of my faculty colleagues say all we do is sit around, drink beer, and make up stories,” he quipped.
Among other projects, he’s helped assess remains of a 15-million-year-old whale calf in Southern California and an ichthyosaurus, similar to a porpoise, unearthed near Lake Shasta.
After hearing a bit about what Francek uncovered, Shapiro made the trip to the foothills last September. The site is on the 28,000 acre watershed owned by East Bay fringing the utility’s Camanche and Pardee reservoirs near Valley Springs.
Shapiro did not have high expectations. Aside from a fossilized horse tooth, there had been few discoveries in this part of California.
Yet on his first day on site, Shapiro viewed dozens of fossils which Francek had already discovered and carefully tucked back into the earth, awaiting the professor’s inspection.
He’d also seen the petrified tree that had been ravaged by looters.
“Within a few hours, we’d seen the ankle of a camel, a small skull, several tortoise shells, and the jaw of a rhino with a tooth. It was terrific, and I said, ‘this site has to be immediately protected.'”
A bestiary fantastic
Francek is fond of a credo, favored in ranger circles:
“You catch it, you clean it.”
After Shapiro and his team arrived, Francek could have stepped back.
Instead, he redoubled his commitment, taking on the role of project coordinator. He’s immersed himself in the study of paleontology, devouring numerous books and scientific papers.
Last October, Francek and Shapiro, as science team leader, organized a major dig including East Bay employees, scientists and Chico State earth science students.
“We wanted to attack it intensively, to make sure we gathered what we could while we could,” Shapiro said.
With shovels and power drills, with hammers and chisels and even leaf blowers, they went at it, revealing a bestiary fantastic that included:
- Rhinos, which crossed into North America from Asia and became extinct in North America about 5 million years ago.
- Mastodons, much like elephants, with long, arcing tusks.
- Three-toed horses.
- Gigantic camels, large as giraffes, which were actually native to North America 25 million years ago – though without the signature hump.
- A gomphothere, like an elephant, but with four tusks. To extract a 350-pound gomphothere specimen, workers had to use a backhoe.
- A baby tapir, a pig-like creature now extinct in North America but still found in Central and South America.
- Remains of giant tortoises, indicating the region may have been warmer than previously suspected.
- There were bones from a fish and a bird, still unidentified.
Most of the fossils were from grazers, Shapiro said. The search continues for predators. During the Miocene epoch when the unearthed animals lived, giant dogs, known as Bear Dogs, and Saber-toothed cats lived, too, and devoured the flesh of the grazers.
While no big dogs or cats have been found yet, the remains of a small weaser-like creature were.
Another remnant of an apparent meat-eater has been taken from the site.
“It’s a pile of petrified poop with crushed bones in it,” Shapiro said.
What hasn’t been found, and won’t be, he said, are the remains of dinosaurs, which lumbered around when most of California was underwater, a good 50 million years before the Miocene time.
It’s quite unlikely the trove contains any human remains, as sapiens came on the scene perhaps 12,000 years ago in California, long after the camels and rhinos and mastodons perished.
Still, the variety of fossils, their relatively good condition, and their sheer number make the Mokelumne site uniquely important, Shapiro said.
Mudflows and jigsaw puzzles
The Miocene was a time of great geologic violence in California. As Shapiro describes it, the animals dwelled on a coastal plain, the shoreline probably running along what is now the western edge of the Central Valley. To the east, where the Sierra are now, volcanoes erupted, spewing lava and creating massive mudflows.
In fact, Shapiro says the creatures were likely not inhabitants of the area where their bones were found. The fossils are mostly, he said, “disarticulated” – that is, they are individual pieces, not whole skeletons.
That shows they likely were pushed by mud or lava – or a blend – to the spot where Francek found them.
“They came from somewhere else, but not too far, because they are still in good shape,” Shapiro said.
If you were to view California in its entirety from high above, in terms of prehistoric knowledge, the state is like a jigsaw puzzle. There have been fossil discoveries, big ones, in just a handful of locations.
“The discovery on the Mokelumne is a new, sizable piece of the puzzle,” Shapiro said. “It will fill in a very large blank.”
Beyond the initial discovery site, researchers have found fossils dispersed in a lengthy geologic vein along the Camanche-Pardee corridor, reflecting both the richness of life in the overall region and the immense flow of mud or lava.
That vein, according to Shapiro, may stretch for miles.
Fossils get a beauty treatment
The Gateway Science Museum, on the Chico State campus, is a spa for fossils. Here, they are pampered, cleaned and strengthened.
It’s a process that demands an eye for both detail and esthetics.
Sean Nies has such an eye.
A geology and paleontology assistant at Chico State, Nies helps run the paleo spa. His academic background includes both science and art.
Nies joined Shapiro, his boss, at the Mokelumne site, where the fossils were exhumed. Most were brushed off, wrapped in aluminum foil and either marked with a suspected identity, such as “tortoise shell,” or with the initials “RB” for random bone.
The biggest objects, such as the skull of a gomphothere, and some of the most fragile specimens, required more work.
Trenches were dug around those pieces and they were swaddled in burlap, then smeared with plaster. Once the plaster dried, the fossils, then safe in a hard shell, could be moved.
Most of the Mokelumne fossils are making their way to the Gateway Museum, a paleo lab, fossil storehouse and exhibit hall combined.
On a recent day, Nies was using an acetone solution to clean the sizable tusks of either a mastadon or a gomphophere – the scientific team is still trying to figure out which.
That’s not unusual; rib bones, for instance, are often set aside or placed in storage, as they are pretty common and it can be difficult to determine their species.
Teeth, on the other hand, are like fossilized gold. Their size, shape, color and texture often lead to a reasonably quick and certain identification.
Nies approaches his work with near-reverence.
After all, by Shapiro’s estimate, the fossils Nies touches are likely 8 to 10 million years old. There are no complete skeletons from the Mokelumne, at least not yet. So Nies typically works with individual fossils or clusters of bone. If the bones haven’t been identified in the field, he will attempt to do that in the lab. He will clean the fossil, in some cases leaving a crust of the dirt or rock – the matrix – in which it was discovered. The residual matrix can make for a more authentic display.
Nies sometimes even sketches the specimens.
“By sketching, you have to really study the fossil, look quite carefully at the shape, the texture, the coloration,” he said.
The sketches help him imagine the animal from which the fossil was obtained.
“It’s not hard to see the beauty in these, the elegance, the way the bones fit together,” he said.
There is one telltale sign Nies and others always look for on the bone: teeth marks, signs of predation or scavenging.
To strengthen delicate fossils, Nies painstakingly paints them with a mix of acetone and Butvar, a plastic resin.
He’s prepping the largest and most unusual of the bones for an exhibit planned at the museum in September.
Yet the bones keep coming. In the museum storehouse, there are plastic bins full of of fossils wrapped in aluminum foil that haven’t been opened, analyzed or cleaned yet.
In coming weeks, they will all be placed on tables for a massive sorting by species. All the camel ankles will go in one spot, the tortoise shells in another, and so on.
Eventually, the most prized fossils will reside at the UC Berkeley Museum of Paleontology. Shapiro said there may be enough fossils remaining to be shared with schools and museums, perhaps including the Worlds of Wonder museum in Lodi, for further study and display. The fossils remain the property of the utility.
How many fossils have been pulled from the East Bay lands?
No one is quite sure, but the number is surely in the hundreds.
The quest continues
The Mokelumne vein is not played out. Nearly every week, Francek discovers new bones. In fact, nearly all of the items wrapped in foil at the Gateway storeroom were found, packaged and sent in by Francek; he’s responsible for 90 percent of the fossils found so far.
And with each new fossil are the questions. Horse? Camel? Rhino?
How old? Where from? How did it live and die?
One oak leaf fossil has been found, and there could be more flora recovered in the months to come. Plants can often reveal more about a specific environment than animals, Shapiro said.
“That’s because animals can move around a lot. Plants don’t,” he said.
The search for big predators continues. Even lions may have roamed the grassy plains of California once. And maybe, just maybe, entombed somewhere in the Mokelumne complex, there could be an entirely new species.
As for the ranger who made the discovery, the ranger who conjured beasts great and small from the stone of the foothills, he is ready for a break.
“For ten months, my brain has been lit by this,” Francek said. “I have been consumed. I’d like to take a little time off with my wife, maybe read something by Steinbeck instead of another scientific paper.”
A break is deserved, no doubt.
But he made the discovery, and now the discovery dwells within him.
If there is a lion to be revealed, a giant Bear-dog, or something never found before, he will find it.
After all, as the old ranger saying goes:
You catch it, you clean it.