Researchers study largest ever Green River mammal fossil

LARAMIE — A rare fossil discovered near Kemmerer — of what is possibly a new genus and almost definitely the first of its species found in the area — is being prepared for further study with help from a wide range of individuals in Wyoming and beyond.

The tapir-like, or tapiromorph creature — preserved for roughly 50 million years in the Green River Formation — was discovered in 2016 by Rick Hebdon, the owner of Warfield Fossil Quarries, and examined by the late Duke University paleontologist Gregg Gunnell.

Gunnell determined the fossil could be an ancestor — and was likely a close relative — of modern rhinoceroses or tapirs, Wyoming State Geological Survey Director Erin Campbell said.

“Since we hadn’t recognized a tapir in these rocks before, they understood that this was potentially significant scientifically, so they turned it over to the geologic survey and we contacted our Fossil Advisory Board,” she said. “They agreed that this could provide some interesting information about the origin of tapirs (and) what areas they may have inhabited at various times throughout geologic history.”

As an ungulate with an odd number of toes, tapirs are closely related to rhinos, horses and zebras. Campbell added the discovery of a tapiromorph in the Green River Formation — a first for the fossil hotspot — could shed light on the evolutionary history of some of these modern animals.

“That’s part of what’s so exciting about this discovery — we don’t know where that will lead,” she said.

Fossils can be difficult to identify, but various experts have examined — or plan to examine — the Green River tapiromorph, using a wide range of methods, aiming to learn more about the mysterious fossil and contribute to its eventual identification.

One somewhat surprising partner in the investigation is Ivinson Memorial Hospital.

The slabs of rock in which the fragmented fossil is contained were sent to the hospital’s imaging department, where Jerry Rice, the department’s assistant director, helped CT scan and X-ray the material, using the same devices more frequently used to study patients.

“We’ve done a lot of work with the University (of Wyoming),” Rice said. “Various groups over there — whether they be the archeology group or paleontology folks, the cadaver lab — every now and then, they have something they would like to be able to run scans on or do X-rays on.”

So when the opportunity came to help with a potentially historic fossil discovery, Rice said he jumped at the chance.

“From my perspective, the excitement comes from trying to image something we’ve never imaged before,” he said. And we don’t know what the outcome’s going to be when they bring these over … It’s always neat to X-ray something like this because you don’t know what you’re going to find.”

The scans will help geologists identify fossilized material within the rock, but it won’t be the last time the Green River tapiromorph is scanned.

Out-of-state researcher Mike Eklund is currently preparing the specimen for further study by taking microscopic photos of it from various angles. The goal is to detect detail and search for the presence of soft tissue fossilization — which would be helpful in identifying the preserved creature.

UW Geological Museum and Collections Manager Laura Vietti said the fossil — the largest mammal ever discovered in the Green River Formation — is rare because most fossils discovered in those ancient lake beds are of fish.

“It’s really rare to find mammals or non-lake-dwelling creatures in the deposit,” she said. “It’s a unique specimen that’s really well preserved.”

Vietti added the fossil, depending on its identification, could lend credence to North American origins for the modern tapir, which is found in Central and South America, as well as Asia.

Members of the public can follow the fossil’s identification process at the geological survey’s website, www.wsgs.wyo.gov.