Two stories down in the catacombs of the Field Museum of Natural History, Jack Wittry slides open a handmade wooden drawer. There are thousands of such drawers that visitors never see — in row after row of towering, metal cabinets.
These drawers hold more than 63,000 specimens that were dug up 50 miles south of Chicago over a 200-year period. Hammered open by people like Wittry to find a prize inside, they represent one of the most spectacular fossil beds on the planet: the Mazon Creek lagerstatte, or mother lode.
Wittry lifts a two foot-long dagger-shaped rock from the drawer. It is 300 million years old, twice the age of the dinosaurs upstairs. The rust-colored stone is split into two halves. On each half is an imprint of an extinct conifer leaf in exquisite detail. The neatly typed tag identifies it as Cordaites borassifolius and credits “J. Wittry.”
A fossil hunter found all eight pieces of it while wading in waist-deep creek water and feeling the bottom with his bare feet.
The wader, Daniel Holm, is from a Morris family that has hunted and sold Mazon Creek fossils for 60 years. Wittry, a self-trained amateur paleontologist, has been at it for just as long, starting on his eighth birthday, when he was gifted a box of fossils containing a fern, labeled only “Morris, Ill.” The museum staff calls him a “super volunteer,” having identified more than 18,500 Mazon specimens and published three books. At 69, he still comes in twice a week at 6 a.m. to study fossils.
“I guess I’m addicted,” he says.
Wittry has done as much as anyone to link the distinguished scientists at the Field Museum with a colorful group of characters: earnest fossil nerds, buyers and sellers, suspicious hoarders, wealthy dilettantes and scrappy collectors who test the outer bounds of legality. They do it for the love of the chase, for science, for money and for reasons unknown. Their contributions have made the Field’s collection of 123 plant species and 330 animal species from Mazon Creek world-famous.
Collectors want quantity; they want quality; they want something no one else has. And their fervor to discover has driven prices and egos sky-high in today’s commercial fossil market.
When stegosaurus is a status symbol
Owning a dinosaur is now a status symbol, and the more that people want one, the higher prices go. Last year, billionaire financier Ken Griffin, whose name is on the exhibit housing the Mazon Creek gallery, paid the highest price ever for a fossil: $46 million at Sotheby’s for a stegosaurus named Apex. (Apex, which sold for about 10 times the anticipated price, is now on long-term loan to New York’s American Museum of Natural History.) That deal followed the 2020 auction sale at Christie’s of Stan the T. rex, which went to a buyer from the Middle East for $27.5 million.
Rising prices have spawned a new class of interested party: the commercial paleontologist. Griffin’s stegosaurus was dug out near Dinosaur, Colorado, by a man named Jason Cooper, who bought the land to find and sell bones to meet the heightened demand. This extremely lucrative private market can handcuff museums and scientists, who then have to rely on others for access.
Northern Illinois doesn’t have any dinosaurs, and the fossil trade in Chicago’s back yard isn’t as lucrative. But it’s alive and well.
For Field Museum curator and paleontologist Arjan Mann, the Mazon Creek fossils offer a window into the magical mysteries of evolution. Recently, he and two students were plumbing the secrets of a 300-million-year-old salamander ancestor from a rock imprint using CT scans and electron microscopy. The fossil had been donated by the former owner of Dave’s Down to Earth Rock Shop, Dave Douglass, and his wife, Sandra.
The Mazon fossils hold a particular fascination because they expose the soft parts of a specimen in fine detail at various stages of its life cycle. In another example, Mann pointed to an egg with a visible embryo inside. The animal body is gone, but a three-dimensional imprint remains inside the rock that formed around it, called a concretion.
Work like this seeks to fill in critical evolutionary gaps, helping scientists explain how fish transitioned “from fins to limbs” and walked onto land. The story told by these Carbon Age creatures is nothing less than the emergence of the first reptiles and amphibians, which led to dinosaurs, to birds, to mammals and, ultimately, to us.
“Mazon Creek fossils are extraordinarily important to studying the evolution of vertebrates,” Mann says. “A lot of these lineages survived through to today.”
Perhaps Illinois’ most famous find is the Tully Monster, now the state fossil. In 1958, pipefitter Francis Tully unearthed the half-fish, half-reptile with two eyes mid-body and toothy jaws on the end of a long neck. The strange creature was one of paleontology’s greatest mysteries until it was classified in 2016 as a backboned ancestor to the lamprey.
Feuds, lawsuits and bidding wars
No one is going to get rich off selling Mazon Creek fossils. Adam Holm, 62, father of Daniel, certainly hasn’t. However, you can find his Mazon fossils on eBay, at the seller page fossilman-2008. Right now, there’s a Tully Monster going for $500 and crab going for $125; ferns are a bit more affordable, at $25. When he has a really valuable one to sell, like an arachnid, Holm calls up his list of heavy hitters, including collectors in other countries, who are willing to pay as much as $6,000 for a specimen.
“I got enough buyers,” he says. “I don’t even need no more. They want what I’ve got.”
Holm’s large yard in rural Grundy County is strewn with hundreds of white and green plastic pails filled with water or ice. Wittry calls it a “bucket farm.” The fossilized rocks sometimes pop open on their own if they have frozen and thawed several times. The Field Museum used to have its own bucket farm on the roof of the hundred-year-old building until the weight of it caused a leak.
Most of the museum-quality Mazon fossils were found and collected by amateurs, including Holm’s parents. Schoolchildren, scout troops and retirees have been picking up concretions around the small towns of Morris, Braidwood and Wilmington for more than 100 years. The craze took off in the 1940s, when fossils were dumped in huge open spoil piles during strip-mining operations for coal.
The mines eventually played out and were backfilled; the gold-rush days ended. A few public properties around the nuclear plant still turn up concretions, but the most productive spot is the Mazon Creek itself, which continues to churn up the fossil bed through periodic spring flooding and the natural freeze-thaw cycle.
Access to the creek fossil bed has been the subject of a long-running feud. Wittry, who knows and gets along with Holm, says the creekside neighbors are in a “Hatfield-and-McCoys type of situation.” Over the past two decades, the sheriff has been called in repeatedly to try to referee; there have been court proceedings involving charges of trespassing, stalking and stealing fossils.
Tired of being hassled by other property owners and the sheriff while paddling up and down the waterway to collect fossils, Holm got himself a lawyer and sued.
“Eight years they’ve tried to keep me off the creek,” Holm says.
The case, Holm v. Kodat, went all the way to the Illinois Supreme Court, where in 2023 Holm lost in a 4-1 ruling. Riverside property owners own the land under the water, thereby controlling access to the water, the court said, citing hundreds of years of common law.
Holm took a break for a few years, but today he’s back collecting from his two riverfront properties, shuttling back and forth in his kayak and making a living. He welcomes an arrest, he says, because he would have another chance in court to challenge the law.
“There was one year I got 11 spiders,” he says. “It’s fun seeing what comes out of every rock. It grows on you.”
U-haul paleontology
For his part, Wittry tries to stay on everyone’s good side, he says. He never knows when a rare fossil or even an entire collection might come his way.
“I deal with everybody,” he said.
Wittry’s biggest score for the Field Museum was the largest collection of high-quality Mazon Creek fossils in the world, held by Thomas Testa, who lived in nearby Carbon Hill. It had been appraised at close to $100,000, Wittry says, but the museum never persuade a conspiratorial Testa to donate his haul.
Then, out of the blue in 2015, Wittry got a text message: “You’ve got 24 hours to come get them.”
Another text came in: “Time is running out.”
Wittry called Testa, who repeated the ultimatum: 24 hours to take the entire collection or Testa would throw them in a bonfire and burn them.
Everyone Wittry knew at the Field Museum was on vacation. There was no one to authorize the transfer or to help load it up. So, he and a friend rented a 15-foot U-haul and, in three trips, moved the literal tons of fossils to his garage.
Wittry donated all of it, no charge: 7,000 separate specimens that included 5,000 different highly sought-after animals. The one-of-a-kind holotypes, or representative fossil of a species, and other high-quality specimens are on display in the Griffin Halls of Evolving Planet exhibit, which recreates the hothouse swamp of the time on the second floor.
The visitors rushing past the Pennsylvanian Age “coal forest” to see SUE the T. rex may never know the long and twisting chain of provenance behind the museum’s Mazon Creek mother lode.