James Sanderson was enjoying a hike through beautiful badlands near Kemmerer when something caught his eye. It was a bone-white streak jutting out of an embankment of loose, brown earth.
“I was more interested in the riverbank rocks,” he told Cowboy State Daily. “There are a couple of ancient creek beds layered over the top of the softer, pinkish sandstone when I saw the bones.”
Sanderson spotted several long, narrow, white bones. They were articulated, connected as they would have been in the animal’s skeleton.
Not knowing what it could be, Sanderson took photos of his odd discovery.
Then, he left it alone.
“Once I saw it, I took photographs and that’s all I did,” he said, explaining he didn't want to touch them. “I wanted (to report it to) the Wyoming State Geological Survey so they could come take a look at it.”
Sanderson sent an email to the Wyoming State Geological Survey (WSGS) to inform the agency of his find. Bryce Tugwell, the WSGS’s media and communications manager, said there will be “a lot of unknowns” about the find until an experienced eye can examine the spot.
“Our specialist is waiting to connect with paleontologists from the Bureau of Land Management and National Park Service, who will be looking at it more closely in the field,” he said.
What could it be? Sanderson has no idea, but he has a few guesses.
“I think it’s a foot,” he said. “It looks like a foot, but it could be an antelope leg that some birds packed on top of that formation, for all I know.”
When, Where And When Matter
There are a lot of fossiliferous rock layers in southwest Wyoming, containing everything from dinosaurs and trilobites to the earliest horses and primates.
That’s why paleontologists take any potential find seriously. Some of the most significant fossil discoveries in Wyoming’s history have come from the rocks surrounding Kemmerer.
Sanderson isn’t a geologist and doesn’t claim to be. However, he knows enough to recognize his position in the geological timeline.
“I’m guessing (the rock layer) was a lot older than mammals, if it is something,” he said. “All I know is that the Green River Formation was several hundred feet above it on the mountaintop.”
The Green River Formation preserves the flora and fauna from the Eocene Period, roughly 52 million years ago. It’s a world-famous formation because of its incredible preservation of fish, turtles, salamanders, birds, and the early ancestors of horses and primates.
That isn’t the only layer of interest in southwest Wyoming. Matthew Borths, a paleontologist and curator of fossils at the Duke Lemur Center Museum of Natural History, has been searching for “the start of the primate story” in the Bridger Basin.
“The primate story starts in North America, and some of the best specimens from the story have come from Wyoming,” he said.
Borths has been focused on the Bridger Formation, “the Madagascar of the Eocene.” It’s from the same period of geologic time, but slightly younger than the Green River Formation.
The best species of Plesiadapis, the earliest known primate-like mammal in the fossil record, has been excavated from this formation.
When Borths looked at Sanderson’s photos, he was similarly unsure what to make of them. The first thing would be to identify the rock formation, which is challenging to do from photos alone.
“Without a little more information on what rock formation it comes from, it's a little hard for me to diagnose,” he said. “It doesn't look like the Bridger Formation, which is the rock layer I am most familiar with.”
Borths believed the bones might have been in the North Horn Formation, a rock layer with extensive exposures in central and eastern Utah. It straddles the boundary between the Late Cretaceous and the Early Paleocene, preserving the moment of the Cretaceous-Paleogene (K-PG) extinction event that wiped out most of the dinosaurs.
However, Borths acknowledged that he’s “not an expert” on the North Horn Formation, and he was only making an educated guess based on Sanderson’s photos.
Regardless, the bones are compelling.
“That's a beautifully articulated foot from some really cool exposures,” he said. “Any specimen that associates multiple bones together is a significant discovery, but I don’t know what it is right off the bat.”
A Small Letdown
Laura Vietti, the geological museum and collections manager for the University of Wyoming, weighed in on what was found in southwest Wyoming. After looking at the photos, it seems Sanderson’s guess wasn’t far off.
“I double checked with a colleague of mine, and she helped me confirm that it’s not a fossil,” she said.
Vietti didn’t disagree with Sanderson or Borths’ geological assessment. The bones are sitting in an Eocene rock layer, but they don’t belong there.
“The outcrop looks very Eocene to me,” she said. “While one can get articulated specimens from the Eocene in that area of the state, it’s very rare. Plus, if it is Eocene, this would be the wrong kind of animal to be found in situ.”
The articulated specimens Vietti referred to came from the Wasatch Formation, another Eocene formation that’s older than the Bridger and Green River formations. A menagerie of primates, horses, and other mammals have been identified from this formation, but their fossils tend to be very fragmentary.
However, Vietti didn’t need to compare these bones to fossils from the Wasatch Formation. From what she can see, they aren’t fossilized at all.
“If you look closely, you can still see some connective tissue,” she said. “That’s the smoking gun that it’s recent. It does look like it’s somewhat buried/interred in the sediment, but it doesn’t belong there.”
Vietti described the sediment as an “Eocene paleosol,” a layer of prehistoric soil that hasn’t lithified into rock. That would explain how the bones of a much more recent animal could get stuck in a 56-million-year-old formation.
As for the owner of the bones?
“It’s the rear leg of a modern coyote or fox,” Vietti said. “It’s hard to tell, especially not knowing where on the hillside it was found, but it likely died on top of the outcrop and slid down in a rainstorm.”
Taking No Chances And Every Opportunity
Even if this strange discovery is from a modern-day animal, it’s worth verifying. Tugwell said that Colby Schwaderer, the WSGS’s paleontology specialist, intends to visit the spot where Sanderson spotted the bones sometime next week.
“From what we know, it’s an interesting discovery, and it does have potential, but there isn’t enough information yet to confirm anything,” he said. “We’ll need to wait for additional evaluation before offering more details.”
Sanderson’s discovery might not be as exciting as a prehistoric primate foot or the remains of some otherwise unknown species from the Eocene, but he kept his excitement in check,
“I think it’s interesting, but I’m not holding out any great hopes that it’s something special,” he said. “I left the items in the matrix undisturbed and will not disclose the location until WSGS has had a chance to study the items.”
The important thing is that Sanderson left the specimen in place, contacted the experts, and provided them with the necessary information to visit and investigate for themselves. That’s how many significant paleontological discoveries are made.
Sanderson, an Evanston-based lawyer “in real life,” is just happy to contribute. This might not be Wyoming’s next big fossil find, but at least he’s helped the experts and reported his find through the proper channels.
That’s how history’s made, when it’s made.
“The WSGS has been very communicative and assured me they will be on it straight away,” he said. “No matter what it is, it’s a very interesting formation with a surprise.”
Andrew Rossi can be reached at arossi@cowboystatedaily.com.
