This is a view of a covered fossil fish as seen under oblique light. Fish like these
are ideal to collect because the skeleton is still preserved underneath several layers
of sediment and careful preparation to expose the skeleton can take place in a controlled
preparation lab. The oblique light at night highlights bumps in the rock, making it
easier to see the hint of skeletons, especially their backbones and skulls. (Claudia
Richbourg Photo)
Laura Vietti recently took some of her students on a trip back in time to Wyoming’s
Green River Formation, where Eocene-era fish once swam; bats and birds flew; and giant
mammals and crocodiles roamed.
“The fossil lake sediments preserved in the Green River Formation preserve some of
the best fossils in the world,” says Vietti, museum and collections manager for the
University of Wyoming Geological Museum. “The unique environment of the fossil lake
prevented scavenging and promoted quick burial, which led to fossils preserved in
great detail including scales, feathers, insect wings, flowers and more.”
During its field trip from July 18-21, the research group, made up of Vietti and a
handful of UW students, visited the Green River Stone Co. quarry, Rick Hebdon’s state
fossil quarry, Fossil Safari quarry and American Fossil quarry, which are all located
in and around Kemmerer.
“One of my primary goals of the field trip was to educate my students on the past
Eocene lake environments and how they evolved through time,” Vietti says. “We went
to several outcrops and quarries from different paleo lake depths, as well as a paleo
shoreline to see how the fish species, fish preservation and rock type changed with
depth. Fish fossils tend to be less intact in the shallower environments and better
preserved in the deeper environments.”
The most common vertebrate fossils are fish. During its excursion, the group primarily
found Knightia, Wyoming’s state fossil, named after UW’s first geologist, Wilbur Knight; and Diplomystus. Both are related to modern-day herring. Although rarer, Wyoming’s Green River Formation
boasts the country’s best-preserved Eocene bats, birds, caimans, crocodiles, dragonflies,
ferns, mammals, snakes and turtles.
“One quarry owner gave us a once-in-a lifetime experience by taking us on a night
excavation where they wait until dark, turn on large floodlights and search for fossils
in the rock using oblique light,” Vietti explains.
Fossils in the deeper lake layers are best removed if still covered by sediment so
that careful preparation can be conducted in the prep lab. Bones of these specimens
are not visible to the naked eye. To locate the specimens, the group looks for bumps
in the rock.
“Quarry operators have found, over the decades, that the best way to find these bumps,
which are usually the backbones, is by using oblique lighting at night,” Vietti says.
“Subtle height changes in the rock, usually due to an underlying backbone or skull,
become much more apparent under oblique lighting and cast a shadow, which otherwise
would be untraceable during the day.”
A group of UW students on a UW Geological Museum field trip was recently filmed at
several Green River Formation quarries, including Rick Hebdon’s state fossil quarry
(pictured here) for an upcoming Wyoming PBS special, which is estimated to air in
2022. (Laura Vietti Photo)
Vietti’s group helped discover several large fish, which included Diplomystus, Mioplosus, Priscacara and Phareodus.
The last day of the trip, at the American Fossil quarry, provided the group a rare
find -- a swimming trace fossil, which quarry owner Patrick Hogle donated to UW’s
research collection.
“The trace fossil is a curved line in the rock from where the bottom tip of the tail
dragged in the sediment as it was swimming, causing a curved line,” Vietti explains.
“They are rare because they are very faint and, often, aren’t preserved or recognized.
We hope to have it on display within the next year.”
During the trip, a producer working for Wyoming PBS joined the group and filmed the
activities for a documentary called “Fossil Country.” The documentary, which is estimated
to air sometime during 2022, will highlight the synergy of the fossil quarry owners,
tourism, research and community, Vietti says.
The discoveries Vietti and her group made will be made available to the public next
spring, when the UW Geological Museum holds its Fossil Fish Festival. The collaborative
outreach event is free and open to the public, with the target audience being school
kids.
“The festival highlights the Green River fossil fish by providing each visitor with
their very own fossil fish specimen,” Vietti says. “And we show them how to expose
or prep the fish skeleton, collected by the museum in the quarries on our fossil fish
field trip, among many other interactive activities.”
UW students who participated in the field trip, listed by hometown, are:
Colorado Springs, Colo. -- Alec Wallen, a senior majoring in geology and environmental
systems science.
Mantua, Ohio -- Austin Shaffer, a senior majoring in zoology and environmental systems
science.
Monticello, Fla. -- Claudia Richbourg, a Ph.D. student in the Program in Ecology.
Prescott, Ariz. -- Lily Jackson, a postdoctoral researcher in geological science.
Stevens Point, Wisc. -- Will Rosenthal, a first-year Ph.D. student in the Program
in Ecology.
